I think I will not let him make this upgrade as a 5 year payoff would require over $100/month additional rent.  

If the drywall cracks in the next year or two, or the doors start to stick, then you likely have a larger settlement issue going on, and will likely need to call a foundation repair contractor. 

Hi Kwanza,Bay Tek (650-204-1512) would be a great starting point, but I’d also recommend reaching out to Adler Builders (650-398-9030) and Mission Home Remodeling (415-855-7269) for comparable bids.In San Francisco, you’ll need a licensed General Contractor (GC) to pull the necessary permits.

Being a lender for 10 years, all is that we required from the title company and the lender is that a notarized close was to take place. 

Unfortunately NY requires a RE license to wholesale in the state.

OP has less than 3 years experience and it appears he has no mentor, he will learn by taking some setbacks.  

Probably this. california department of Real estate has already nailed two agents for raising rents above price gouging thresholds.. 10k fine plus who knows what kind of license discipline.

2) Their contractor must be properly licensed and insured and we require copies of all this.

You can be sure they will continue to negotiate for, strategize and advise themselves.If the laws are similar where you are, you should consider if you want someone doing those things for you, and whether you are comfortable going toe-to-toe alone with a licensed professional on a $1.25 million purchase.

It will give you their time as a licensed professional, the education they have completed for the current renewal schedule, and any disciplinary action against them.