Sue, overall, a single-family home is a much better investment than a condominium. First off condominiums are the first type of property to drop price wise when the market is bad and the last come back up. Also they typically have an HOA fee which not all homes do. Also your assumption that you get a condo for $50-$70,000 is somewhat correct, however that will be in an undesirable area or in very poor condition. A condo in a decent area that will bring the proper rent will be more toward $100,000.
All in all, single-family homes trump a condominium typically, however you should also consider multifamily units such as duplexes, triplexes, and fourplexes. With a duplex for example, even if you lose the rent on one side, you have rent on the other side help support the mortgage and overhead.
Since I am an investor myself and also help many investors, I would be happy to discuss your short and long-term goals and work with you at no cost if you are not yet working with a Realtor. I also have some great lenders who will pre-approve you at no cost to you, and some great inspectors to make sure you know what you're getting into before you make a purchase. Please let me know if I may be of assistance.
Joe Jarusinsky, Realtor/Master Instructor, Keller Williams Realty, Austin's #1 Real Estate Company, Ranked #1 by Buyers and Sellers (JD Power & Assoc. 2012) Call 512-261-4415