The sole remedy is a return of the deposit, in my experience.

Use the deposit to handle cleaning and repairs, then refund the remainder.

Especially buying and matching from different sources.

Look for the properties that have been flipped/upgraded and match up your subject property with similar inventory.

I want to keep accepting apps until a lease has been signed and I have a deposit in hand. 

At the same time, I want to stick with him because we already "commenced" this project, deposit paid, rapport established, all contribute to a feeling of sunk cost.

Will they add value to your apartments, you could ask an appraiser.They will change the look of the building somewhat.Why are the stair floors black and the balcony floors tan vs matching (???)

Are the rents and deposits the same as a standart commercial tenant? 

When we asked him for these documents, he even said that in 40 years he never deposited any rent money in bank (I think its the norm with mom and pop mobile home owners).

Oftentimes, I see people go into those types of properties with spreadsheet (or worse, their sales agent-assisted) projections, and the projections often do not match up with the reality on the ground.