It has subusers for landlord/property management/tenants/vendors (think maintenance etc.)

Essentially you resign as a W-2 employee, and get hired as a vendor. ( Ideally, for tax purposes, you would start a S Corp or LLC, and your current employer would pay you as a vendor).

My version of the purchase contract is also accompanied with a list of renovation done (or to-be done, by which vendor, stipulating which job comes with warranty, length of warranty, which doesn't - not all of them do).Have you gone over all your questions on the contract with your TK and have them addressed your concern?  

As a consumer of private financing, I've never asked for more than 5-years (in vendor financing this is where the capital gains deferral benefit ends).  

I thought the longer the warranty, the more confidence the vendor had.

The farther it is, the harder it is to manage, show, find tenants, get vendors and inspect3.

As @Luke Anderson eluded to they need some time to make sure funds are clear and if they are paying repairs out of proceeds they need vendor invoices prior to settlement.5.

I usually shop local vendors depending on what it is I am looking for.

We have about 50 of the boxes and used them for prospective tenant self showing and vendor access.

You are more likely could use similar design, same vendors, and subcontractors so that it will not cause you much extra overhead to take care of their projects.