If he has an uncommon circumstance that he would like considered only the lender can provide a worthwhile opinion. 

It's not uncommon to sign a non disclosure for that purpose, like others have stated, but why should he expect you to take on the risk of leasing to him, without knowing anything about what he's going to do?

It wasn't that 20k was unheard of, in fact, it was not uncommon.

In very competitive situations, it's not uncommon for buyers to offer a portion of the EMD that is non-refundable from day 1 (sometimes referred to as "going hard" or "due consideration.")

It is not uncommon to see vacancy and maintenance omitted from their projections or are far understated.

It's not uncommon for investors to have penalty clauses the same way they have bonus ones.Also big box retailers are not necessarily the best place to get your materials and especially labor.They can definitely be good for some things but I wouldn't rely on them as a "one stop shop" kinda deal.I'd look for more local supply stores and subs/trades that can install without the big box mark up.

It’s not uncommon for an HOA to require an approval of the tenant and lease.

I know of 2 attorneys that are primarily RA's and it's not uncommon for them to get 5000 pieces of incoming mail every day,

My primary house is 1900sqft, Zillow has it at 1300sqft so it's not uncommon

It's not uncommon to save 5 figures when going through a tax planning strategy.