I have worked in investment banking, private debt, commercial banking, and private equity all at “prestigious” firms and closed $30bn+ worth of deals.

Especially big name firms. 

Some firms will include Form 3115 with the study.

A lot of management firms paid attorneys to write their agreements and might not feel comfortable altering terms.

It's an interesting article about HOA's and COA's - might be worth a call to the law firm to ask about your rights and if your legal fees can be covered if you win.

The second was to ask about how firm my offer price was. 

Your lack of firmness over time may have lulled this tenant into putting less priority on paying his housing bills.Some tenants are chronically late and pay the rent by mid month, plus the late fees.

I've also read a some books by Calum Ross (but his firm is close to the public it seems), Tahan Aburaneh, Doug Grey, and of course Don Campbell. 

An investment firm contacted me and wanted to start a rent-to-own agreement. 

I’m not sure about the small brokerages but it is my understanding that the larger firms don’t make all that much from the agents, they make their money from their associated Escrow, Title, or other service business for the industry.