Seeing that I have my website up with up and accumulated about a dozen and a half cash buyers, I’d offer them buyers and act as a bird dog until I can actually get a deal under contract. 

It's in a neighborhood that we love and the house is a great fit for us personally but we leveraged FHA financing and the local state housing authority grant program to get into the property for no money down and a PITI payment of $950/month.

I wouldn't touch this house unless I had a pile of money to burn, and a serious network of good tradesmen.

I started with single family homes thinking that experience would help me invest in apartment buildings, but I eventually learned that you don’t need money or experience to start investing in apartment buildings and a single family track record wont help much.

I just purchased your book on negotiating and a few deal finding books as I’m doing a book every 1-2 weeks.

And as I mentioned, three sales on the property had already fallen through, probably due to the same title issues.  

When buying a property using owner financing does there have to be a deed of trust and a promissory note?

It's completely paid off and a Zillow search has it probably valued around $300k. 

Should I pay for 30 years and cash flow (leaving more money for other deals) or sacrifice current cash flow in order to pay off in 5-7 and have greater cash flow later and a paid for property?

Marketable title is title that doesn't have material defects... and as such the buyer cannot claim there is a title problem and refuse to close.