Should I buy more condos for investment?

I'm living in Houston, Texas medical center. The condos in this area is kind of hot. Easy to sell, easy to rent out. my complex
is a very good location, the 2BR&2BA is about110k condo can rent for 1k, the property tax and maintaince cost about 400-450/m, the 1BR&1BA is about 65k-70k, and the rent about 700. Sometimes I'm thinking about to buy few more for investment, but I'm a single girl, maybe is that too much? I know a good handy man who can help me and asks for reasonable fee if there is any problem with the condos. I paid cash for the first condo and my income is not bad. I read one article few days ago, someone says if the rent is the 10% of the house, it is ok to invest.Could anyone give me some ideas?