Acquiring real estate and business assets - seller has no current valuation of either.

Context -
1. Seller claims to have other interested buyers.
2. Banks sometimes quit deals last minute.

Question -
Has anyone tried requesting say 35% contribution from seller towards valuation costs in return for copy of reports?

Seller benefit =
Use of valuation to support price sought from other buyers.

Also welcome -
Any suggestions on avoiding or mitigating scenario of surprise last-minute abandonment of transactions by banks.

Thanks.