Once you own a rental you must kepp it habital for the tenant, meaning always having working furnance, hot water, a roof over their head, etc...A down payment for onwer carry is whatever you can negoiate.

Folks often fall into lifestyles and habits that bring them peace and comfort.

Co-signer or not, if they don't have a job and can't get one quickly, the rent can't / won't be paid.Still may be a good idea to get a co-signer, but I'd put primary focus on employment history and bill paying habits as seen on credit report from when they were fully employed.

Otherwise, if the rehab is minimal to bring up to habitable conditions, you may make an offer of $80k or sub2 or wrap.

The biggest issue I think with long term tenants is habits that you may not want. 

I would recommend the 7 habits of highly effective people and how to win friends and influence people.

They will only work with properties that are deemed habitable and safe.As Caesar pointed out, somebody who can put down cash may be a more appealing buyer, but on the other hand, if you don't have to put anything down, you may be able to come back with a higher offer that beats the cash offer.

I continue to always look myself as part of a habit because those are what I would be looking for as well.

Or habitable?"

Section-8 (if they do the inspections at all) simply makes sure the house is habitable.