Their price isn't ANYWHERE NEAR what their BS website claims they deliver.

He is a stay at home dad so has the time to co-ordinate drop offs (most people want it delivered to their campsite since they don't have large enough vehicle to tow). 

I've heard of mentees that started out cleaning up construction areas on a flip at the end of each work day or picking up supplies at Home Depot and delivering them to the job site.

What does the contract say about the seller being unable to deliver marketable title?

Many of the solutions you have to deliver to get substantial discounts on property would have to be solutions to headaches that nobody else (including the seller) wants to tangle with.If you can't find any compelling problem in this section, you should seriously consider moving on with your life by referring them to some sort of service provider that might be more appropriate for them.

They are very good tenants they asked for permission to buy them before they where delivered.

You could structure it contingent on the property be delivered vacant OR delivered with the current tenants paying market rent.

If either of these were addressed in the agreement, send/deliver a notice of violation per local law and the terms of the agreement.

If you don't use leverage, its very tough to deliver attractive returns to investors.

I'd like to buy new so they won't require much maintenance in the future plus can be delivered/installed.