The condos I am looking at range from $110,000-$140,000.

We found a small duplex within our price range and found it worth it.

A fair interest rate for seller financing typically ranges between 4% and 6%.

As such, there's a wide range of quality in Martis and probably a range in $/sf.  -$600/sf houses (or even $400/sf) are definitely not out of the equation. 

We were super lucky to have hit relatively low rates (15-year 2%-3% range) that we would not see again today.The Dallas property is now rented, giving a almost zero cash flow over a 15-year fixed mortgage, until the recent HOA increase pushed it into the negative side slightly.

You're probably looking in the $400- $500k range.

Rates currently range from the high 4.00% - mid 5.00%'s depending on the asset / borrower / location. 

At the end of seven years, the interest and principal is paid back and I have effectively manufactured $60,000+ in cash. 

(You can't move earlier than a year and get another primary residence.)If you buy a 4br in the $500k range and put 5% down, that's likely $3300/mo or so.

To give some context, my budget is around $300K, so any recommendations within that range would be especially helpful.Looking forward to your advice and suggestions!