Similarly, if you put several Class D tenants in a Class A 4-plex, what do you think will happen to the property?

Similarly, AirBnB might be slow to respond to this but guessing they will catch up.I don't know if JT and Yucca Valley are part of the areas impacted by Newsom's order.

Look at Homes.com or Realtor.com to get an idea what that type of property is selling for (look at the ones Pending or Under Contract)...or, look in the county's GIS system to see what similar properties sold for.Once you have an idea what a fair market value would be, let the landlord (if they're interested in selling) mention their price. 

Similarly, if you put several Class D tenants in a Class A 4-plex, what do you think will happen to the property?

A house that's similar, but 10% larger than another usually isn't worth 10% more.

What are other similar triplexes selling for in the area?

I suspect you would bill in a similar manner. 

JMHO  I use a similar approach to paint sheen.

@Robert Gorra - I've had a similar experience where I've had a really hard time with getting GC's to even give me an estimate, and the few that have have been way overpriced (ie, they want me to put in $20k of cabinets in a budget flip) or have had their prices go up by about 40% and still not give me a firm price when I try to nail down the scope of work.

Gap lenders look at deals similarly to tru private lenders: case by case, risk of deal combined with risk of borrower.