They want to inspect the unit to ensure I removed EVERYTHING.

There have been investors who have told me horror stories about having to open the walls back up in order for them to inspect.

Overall I had no issues with my tenant, and when my brother did an inspection on the property he was happy to see it in good condition. 

Tenants leading him right down there is not ideal but the building department/inspector does have a right o inspect any homes where they have justifiable cause or safety or heath concerns. 

And what kind of contingencies should I put in there (passing inspection, appraising at a certain level, etc.)?

Make sure to find someone that has a lot of knowledge on the housing/rental market, experience with the building codes, inspection/permit process and programs tenants will sometimes use.

Before the virus hit it was really tough to get into a multi family with any sort or contingencies (financing, inspection, and the like).

I will also have the inspection done this afternoon.  

Can I negotiate to decrease the price based on work to be done after inspection?

I would attend local section 8 meetings, call them directly and ask for their rental comps, inspection criteria, and any other useful information.