Let him know you will let October rent go and give him his security deposit back but under no circumstances can he stay. 

I added a 5% misc. in the fix budget already, then rounded up an additional $3k.After you run a report, how do you determine if you're going to move forward or not (especially given there are always so many unforeseen variables)?

Your (his) question just focuses on one issue, possibly to the detriment of his overall financial well-being.Example of what could work under the right circumstances: if he sits on $1M cash, he could invest in a syndication or a JV that buys a distressed apartment complex, turns it around and sells in 3-5 years, for a sizable capital gain.

Do not, under any circumstances, sign a lease with this person. 

Research them for you circumstances and make a plan.

C.A.R. put these procedures in place to protect us from unforeseen or future costly liabilities.    

I don’t know the rest of your circumstances.

My only concern would be waiting so long that interest rates go up (or I get laid off from the current job - or any other unforeseen risk that is slightly less likely to happen with a short period of time due to my current advantages). 

When I first visited Oklahoma I drove through Tulsa and really liked it, however circumstances have brought me to OKC.

Regardless of anything I do believe you should leave about $5,000 in a fund to handle any unforeseen maintenance or any issues that arise.