For example the mortgage industry will typically view three houses on one lot as a "3 unit" property since the word "triplex" isn't to be found in the FNMA guidelines.

VA GUIDELINE?

Quality of MaintenanceThis one ties in importantly to item 1.In depth, first, the quality of maintenance and second, the finishes need to be commensurate with the rent charged (or even slightly better) to make someone feel they are getting good value for their money.First, obviously, your property needs to meet all minimum safety and habitability guidelines—That is a deeper item for a different time, but ultimately, if you are a “slum lord” and tenants do not have access to the bare minimum requirements for peaceful enjoyment of their home, they will be quick to leave.Assuming that “bare minimum” box is checked, you can turn your attention to quality of finishes and general maintenance.First and foremost, the finishes should be commensurate with the price you are asking for rent.Now, the neighborhood and local comparable are hugely important in the decision making here.Is your home in a low income area?

Gambling on appreciation is still gambling.Start with a good cash flow base, in case the gamble doesn't pay off... your mortgage is still taken care of at any rate.

@Kevin Swan Fannie Mae guidelines allow up to 10 mortgages not 4.

It would be a waste of time to go through the whole process only to be denied by the lender because the condo itself doesn’t meet guidelines.

Stick to areas that have had a great reputation for a very long time and leave predicting the future to the guys who have too much money they can risk to gamble.

We place them near hot water heaters, washers, and under sinks.To protect yourself from potential damage, establish clear guidelines in your rental agreement.Here's a clause from ours:APPLIANCES.

Guidelines for residency within the US means, Living and Working in the US full time."  

. - FHA in general has a bunch of anti-investor rules in their guidelines, I'm sure there's something else that I'm not thinking of at present from their 1000 pages of guidelines.