With spreadsheets.I'm a machinist - expect me to be painfully precise.

That would be an extreme amount and I would lose pretty much all the equity I've built up over the years.If I am correct and my cost basis is actually $100k, is my only option to avoid a huge tax hit to attempt a 1031 exchange, or are there any other options available?

I also like the idea of getting a new sink door in exchange for a damaged one. 

@Chuck Cirulli: Investing in exchange traded markets have a lot of exemptions built in for the IRA investor and it is primarily around the fact that you are working through an intermediary (i.e. an exchange) where the buyers and sellers are generally anonymous.

@Jay MirandaIf your partner in this venture will be purchasing the property in cash, you could lend the rehab money in exchange for a (1st position) mortgage (registered against title naturally).

If PMI for rental property mortgages is tax deductible, then is a 20% down payment as important as it would be for a home you would occupy or live in? For a rental property it seems like you can do a lower down, get m...

That possibility is precisely what I want to mitigate.So, upon further research, I found a palatable amount of unpaid taxes -- and the county owned all of the certificates -- no one had bought them.  

You can use standard depreciation, 1031 exchanges, or cost segregation.

Should I encourage my friend to make this investment happen, even if it is without me (or for a small share of it in exchange for assisting him, finding it, managing, etc.) or just wait for a couple of months until I'm in a position to invest my half of cost but risk losing the property?

Using roughly the same amount of money you described from a 1031 exchange, I was able to buy two cash flowing properties right here in Denver this month.