Visit Many Properties & Do Your Homework
Consider and tour many different properties. Figure out what works and what doesn't about each of them for you. Consider the most important things for each one including price, location, condition, and allowed uses.
The importance of location can't be overemphasized (we'll spare you saying it three times). Properties located near universities, hospitals, or downtown areas will generally have a higher value and sell more quickly.
Above all, you're searching for a "fit" with your property. Your situation and needs are unique. The property should be a fit in terms of price, location, uses, and investment required.
Key calculation for any property: It should be in the black after subtracting what's called PITI (principal, interest, tax, and insurance) from the annual revenue earned from rent.
Here are a couple other questions to consider for each property you're interested in:
What is the property currently used for?
What can/can't it be used for?
What kind of rent/income does the property currently generate per year?
What kinds of taxes are there on the property?
What things will need to be replaced or repaired soon?
Why is the owner selling?
How is the area around the property doing? Any major upcoming changes?
Also see this more extensive checklist of questions to ask about properties.