Us cities with the most underwater mortgages:

 Some of the cities with the most underwater mortgages are:
Las Vegas, Phoenix, Modesto, Jacksonville, Tampa, Vallejo, Stockholm.

More about: Doing your due dilligence

Talk to renters as well as homeowners in the neighborhood. You will find that renters can be more will  honest about the negative aspects of the area because they have no investment in it. If you know exactly what  neighborhood, try to visit it at different times on different days of the week to see your future neighbors in action.

Generally speaking if you are a beginner in the  investment property field then the best  is a residential, single-family dwelling or a condominium. Condos are low maintenance because the condo association is there to help with many of the external repairs, leaving you to worry about the interior.

One positive side about single-family homes is that they tend to attract longer-term renters in the form of families or couples. 

One of the reasons why families, or couples, are generally better tenant than one person is is that they are more likely to have a stable finance and pay the rent on time. As a landlord you want to attract this type of demographic.

When you have decided on  the neighborhood, then look for a property that has appreciation   potential and a good projected cash flow.. Look around for properties that are more expensive than you can afford no only the one withing your budget as the real estate agent can often sell below its listing price.

For appreciation potential, you are looking for a property that, with some light renovations, will attract tenants who are willing to pay out higher rents. This will help you to get more for the house if you decide to  sell in the future.. As far as cash flow you to have to make an informed guess. Take the average rent for the suburb you choose and subtract your expected monthly mortgage payment, property taxes (divided by 12 months), insurance costs (also divided by 12) and a good allowance for maintenance. It s very important not to underestimate the cost of these last or you will pay for it once the deal is done. If all these figures come out even or, better yet, with a little left over, then you know its a good buy.

You will find that in every state you have has good and bad cities, every city has good  and bad neighborhoods and even every neighborhood has good  and not so good properties, but it takes a lot of time and research to line up all three. When you do find your ideal rental property, keep your expectations realistic and make sure that you have a clear idea of what you can afford and what your goals are.

What to look for when buying property

• Neighborhoods The quality of the neighborhood in which you buy will influence both the types of  tenants you attract and how often you face vacancies. For example, if you buy in a neighborhood near a university, the chances are that your pool of potential tenants will be mainly made up of students and that you will face vacancies on a fairly regular basis (during summer, when students tend to return back home).  
• Rents   You need to know what the average rent in the area is. If charging the average rent is not going to be enough to cover your mortgage payment, taxes  and other expenses, then you have to keep looking. Be sure to research the area well enough to gauge where the area will be headed in the next five years. If you can afford the area now, but major improvements are in store and property taxes are expected to increase, then what could be affordable now may mean bankruptcy later.
• Natural Disasters Insurance is another expense that you will have to subtract from your returns, so it is good to know just how much you will need to carry. If an area is prone to earthquakes or flooding, the extra insurance can add up and eat away at your rental income.
• Property Taxes  Property taxes are not standard across the board and, as an investor planning to make money from rent, you want to be aware of how much you will be losing to taxes. High property taxes may not always be a bad thing if the neighborhood is an excellent place for long-term tenants, but the two do not necessarily go hand in hand. The town's assessment office will have all the tax information on file or you can talk to homeowners within the community.
• Schools Your tenants may have or be planning to have children, so they will need a place near a decent school. When you have found a good property near a school, you will want to check the quality of the school as this can affect the value of your investment. If the school has a poor reputation, prices will reflect your property's  value poorly. Although you will be mostly concerned about the monthly cash flow, the overall value of your rental property comes in to play when you eventually sell it and retire someday.
  
• Crime No one wants to live next door to a hot spot for criminal activity. Go to the police or the public library for accurate crime statistics for various neighborhoods, rather than asking the homeowner who is hoping to sell the house to you. Items to look for are vandalism rates, serious crimes, petty crimes and recent activity (growth or slow down). You might also want to ask about the frequency of police presence in your neighborhood.
  
• Job   Locations with growing employment opportunities tend to attract more people - meaning more tenants. To find out how a particular area rates, go directly to the U.S. Bureau of Labor Statistics or to your local library. If you notice an announcement for a new major company moving to the area, you can rest assured that workers will flock to the area. However, this may cause house prices to react (either negatively or positively) depending on the corporation moving in. The fall back point here is that if you would like the new corporation in your backyard, your renters probably will too.
  
• Amenities Check the potential neighborhood for current or projected parks, malls, gyms, movie theaters, public transport hubs and all the other perks that attract renters. Cities, and sometimes even particular areas of a city, have loads of promotional literature that will give you an idea of where the best blend of public amenities and private property can be found.
  
• Building Permits and Future Development The municipal planning department will have information on all the new development that is coming or has been zoned into the area. If there are many new condos, business parks or malls going up in your area, it is probably a good growth area. However, watch out for new developments that could hurt the price surrounding properties by, for example, causing the loss of an activity-friendly green space. The additional condos and/or new housing could also provide competition for your renters, so be aware of that possibility.
• Amount of Listings and Vacancies If there is an unusually high amount of listings for one particular neighborhood, this can either signal a seasonal cycle or a neighborhood that has "gone bad." Make sure you figure out which it is before you buy in. You should also determine whether you can cover for any seasonal fluctuations in vacancies.
  Similar to listings, the vacancy rates will give you an idea of how successful you will be at attracting tenants. High vacancy rates force landlords to lower rents in order to snap up tenants - low vacancy rates allow landlords to raise rental rates

Important considerations when investing overseas:

When dealing with an agency is important to make sure you know who you are dealing with:

1: Meet the Team 

Find out who everyone is and understand what their roles. Know who are the people involved with this company.

2: Get referrals:
Get as many referrals as possible, see what they have to say, its hard to always have everyone happy so listen to what the complains are about.

3: Property Management but most important factor for investing is a good solid management team 
How they handle the following:

A: Repairs - 

B: Evictions -   how long to re rent and what cost associated with that ?

C: Payments -How do they processed.

D: Monthly reports (P & L Statements) profit and loss statement...

E: Rehab requirement  (what type of work is been preformed on the property)

4: Real Estate Goals
Have a plan with which will  exactly what you want to achieve with your real estate and how to act if things do go as plan. So many people overlook this important step when buying property.

5: Personally viewing the properties and the Team in action

View the properties and see how the company runs. Try to be there on weekdays so you get a good feeling of how things work.  Videos and pictures are good but not always tell the whole truth about the property.

And last but not least.. always ask for recent sales on the same street that you are buying and make sure that you buy from someone that owns rental houses in the same are to avoid dealing with just another salesman.