There are some questions to be asked:
What kind of loan does the seller currently have on the property?
Most loans have a "Due on Sale" Clause, and if the documents are property recorded at the courthouse, the lender may call the loan due, and most cases, they do call the loan due, which as you can imangine will cause a whole boat load of problems really fast.
Here is a great article to read: http://recenter.tamu.edu/pdf/1754.pdf
The Attorney General also has some good advice: https://www.oag.state.tx.us/consumer/buying_house.shtml
Here is another "Buyer Be Aware" type of article to look at as well: http://www.ntxe-news.com/cgi-bin/artman/exec/view.cgi?archiv
The fact is... there are TONS AND TONS of lawsuits in Real Estate, and a BUNCH of them come from "Contract for Deed" or "Rent to Own" type of deals. You are much better off doing an owner-finance if you just cannot fix your credit enough to get an FHA or other type of loan.
Just go in with your eyes wide open, take the time to read the pros and the cons, and decide if this is a direction you feel comfortable with.
If you have any real detailed questions.. a call to a really good Real Estate Attorney is always wise.
Jason C Campbell
Keller Williams Realty
Chris Hutchinson Real Estate
The Michael Group
Make sure if you want to try this that you hire your own Board Certified Real Estate Attorney to review all documents. One that you pay for yourself and you meet with alone.