This was a full gut renovation, about 70k rehab.

I haven't looked at J's numbers since then to see what has doubled, what has tripled, and maybe what has stayed somewhat close...That being said, if you are looking for very, very borderline useless numbers, plan on $50/psf for a moderate update to $100/psf for near gut remodel.Given that you are already very close to closing, realistically, I would say, you just need to get actual bids for your scope of work.  

Also, our renovations are effectively full guts.  

For example, on what I thought was a relatively simple project in a bathroom reno which was fully gutted down to the studs already, I had more than one quote for over $7k to run pex supply lines and rough in a shower drain and toilet drain off of an existing main stack, all of which ended up costing me about $200 in pex lines, PVC fittings, and sawzall blades.If you need any hardwood flooring repaired, patched, or refinished, you can't beat Dave's Hardwood Flooring out of Blaine - $3k spent with them fully brought one of my duplex unit's original 100+ year old maple floors back to life.If you're putting in any stone counters in your kitchens or for bathroom vanities, Twin City Discount Granite have been awesome to work with, and consistently have the best pricing I've found in the area on fully installed granite and quartz.I also have a great drywall guy, as well as a really good carpet install guy - feel free to DM me if you want either of their contact info!

A similar unit sold for less and he said that one was a full gut.

The moral of the story is: if your gut tells you your PM isn't doing his job, pay attention!

My gut feeling is next time this happens I tell the seller that I won't go along with such a situation.

Your replies align with my cautious instincts!

Might be tough from area to area, but I typically find that homes built before 1950 that were converted from single to multi family are 9 times out of ten - a full gut rehab and way too expensive for first timers.

The more you succeed the more there will be people who will hate your guts for it and will wish to harm you to deprive you of the fruits of your work).