I'd say typically the PM has the contract, and depending on the customer, there are some points that can be negotiated, but normally just minor details on numbers / fees etc.

The form I customized also allows my homeowners to upload pictures of the property to avoid having to go out to the property.

I would not recommend UPWORK for this, or even making a custom site at all.  

I spoke to 3 of the roofer's prior customers, whom were happy with the work.

A little bit about me: I graduated with a BSBA in Business Admin. with a Minor in Entrepreneurship and an emphasis in Sales/Customer Service in 2018 at the University of Missouri-Columbia (M-I-Z!).

Have they explained who the primary customer is?

Customer Service: the ability to calm upset clients or claimants when the claim turns negative.Correspondence: creating and writing documents that are shared with clients, attorneys, doctors, law enforcement, claimants, contractors, etc..

While this adds extra cost and complexity, it allows you to customize the Operating Agreement, not the Articles of Formation, if necessary, for example what if its not a 50/50 split? 

Either close to the customers home (expensive ground/higher rent needed/lower availability of land) or close to their recreation area (less expensive ground/lower rent/more land options). 

There are a few sites that do a good job of comparing different property management software companies, while giving you a chance to look into customer reviews.