Rather it assumes you'll have some nominal vacancy like a couple of weeks or a month for a turn over, a nominal amount of routine maintenance (which is mostly caused by tenants, not the property, so being rehabbed doesn't translate into no maintenance), property management (which you can earn back if you do it yourself, but which you will earn), etc.

That doesn't seem like it fulfills your fiduciary to your client, as there could be a stronger applicant who was not presented due to your process.It would seem that a work-around to avoid any problems with "testers" would be to have the tenant you agree to sign the lease with pay a nominal amount more than other applicants (say $10/mo) so that you had a legitimate reason to select their application over any other.

Which theory did Bernanke favor prior to his nomination?

That should buy you back 10-15% of the gross at a nominal cost... maybe $150 - $200 per pad.

Regardless, it sounds like you're saying that Tim deserves a nominal fee for handling the paperwork and getting the deal done.The question is, how about the buyer's agent?

But I'd be willing to venture it'll be caused by one, or some nomination of the usual suspects: higher rates, economic downturn...

Not this year or last year, but the long term averages over the last 30+ years, certainly long enough time period to capture both up markets and down markets and being careful not to cherry pick your start or end dates to be an up or down market.If after underwriting with those averages and other reasonable projections you still like the investment under nominal scenarios, then you need to stress test your investment to make sure that under any bad (but still somewhat reasonable) circumstance you have the intent and ability to hold onto this property, or at the very lease have multiple exit strategies to sell at profit if you need or choose to.

I've had a seller stuck on price before but was willing to do a type of seller financing that was basically 2% better than commercial lenders would do, a nominal down payment instead of 20% and a balloon term of 12 years instead of the normal 5 years. 

You're clearly thinking in terms of a gross or nominal return.

Me,  not very hard.At $10k NOI, and 10% cap rate, the value of this park is $100k + nominal value of 12 trailers ($3k each) so $120k asking is per the math.