Real estate investing is a team sport and at different points in the game different players will play more important roles.

As Jay and Jamie have stated above, a minimum of 6 different factors play into the pricing, but it is not an all or none issue. 

Use surveys to gather feedback on their experience.When tenants feel valued and respected, they’re more likely to take care of the property and renew their leases, saving owners time and money.Fairness with VendorsVendors play a crucial role in maintaining properties, and treating them fairly ensures they remain reliable partners.

I golf, play a lot of softball, run most days, walk my dogs, do some real estate projects.... stuff like that. 

There is a potential scenario where an outside rescue fund (marketed as preferred equity to new investors) could come into play in many of the projects that appear to be performing especially if they have been paying the pref (via a reserve account stockpiled by over raising funds in the beginning).

I’m building a tech solution that should drive more buyer leads to an agent’s pipeline. But to build this I will need access to NAR APIs. Is there any developer here who can share their experience building with the AP...

I have been playing the multifamily game for almost 10 years now, and the GRM is one of my least favorite methods personally since it ignores so many important factors (steam boiler versus electric baseboard heat as an example). 

I’ve seen situations like this before, and keeping control of the contracts has always been the better play.

You can only play games for so long.Chances are your next door neighbor is an IRS agent and turns you in when your tenants blocks their drive or some other random event disturbing your IRS neighbor.ADU catches fire and your insurance won't cover you, because it was an illegal and unpermitted structure.The city inspector told the last guy not to build or rent it, and is now pissed and wants to make an example of you and just red tags the whole property and no one can occupy for the next 1-2-3 years while you wait for a hearing.Then when you get the hearing, "staff" recommends you tear the whole structure down, and if you still want an ADU, you can apply for a permit and rebuild it.Your tenant quits paying rent and won't move out and you can't evict them, because there is no valid lease and they're just your "roommate".Probably a dozen other bad things can happen to you when you do stuff like this. 

Amortization length along with any DSCR requirements comes into play also to determine what kind of down payment requirement you may have to meet.