Where to put 20k?

[Matthew Harrison]

My wife and I are coming into a lump sum of 20k and would like to invest in realestate. I currently have one rental house in metro detroit that I share with my father. It is rented to a friend for 700, and we bought the house for 45k. My question is: where is 20k most effectively invested? I am interested in both long term wealth, and cash flow. I am anxious to own 100% of a rental, but personal finances don't allow me to get a mortgage. In my area I could get a rental ready home from 60k that would bring 900/month on average. Assuming I have someone else (my father) aquire another mortgage, should I look for another house like I have? Find a fixer that would possibly require the entire 20k? Find multi unit where 20k is needed for downpayment?