I want this project to run smoothly, but I can't afford $150k for this project.  

What documents or verification do I ask for from buyer to make the transaction go smoothly and professional as the seller?

You can come up with the best projections and budget, but not everything is going to go smoothly.

It was a smooth process.

I currently have two houses going currently but not going very smoothly.

It was fairly smooth.

At first I did it out of necessity as property managers in my area were charging in the range of 25-35% of gross rents and at those fees, it cut drastically into profits.Now that I've been self-managing for a little over 2 years, I've created systems to make things very smooth and I'm so glad I made that decision. 

I learned so much from that first purchase that my second one went smooth all due to having a better team in place.  

As far as my REI experience goes, I feel like I have a pretty solid start for my age.I purchased my own home as a forclosure roughly 3 years ago and have been able to pay it off after selling my business.My home unfortunatly is not worth very much(under 40k).I also assisted my brother in purchasing a house for his family last year off of an auction site.It went pretty smoothly for the most part.

I just want it to go super smooth (seems so far...cash buyer) for both us and all aspects to protect or have a good outcome .