If you don't either send it to me, or donate it to a worthy charity, but don't let your tenants keep it, they're not doing anything to deserve that kind of paycheck.And you'll say - 'But they're good tenants'....No kidding, they're getting a free ride, everyone will be a good tenant for that kind of discount.

How would taxes work if I receive money from a wealthy friend who isn't a "Private lender", but just someone willing to donate cash to help me with a fix and flip.

You can sue them and get a judgement, but if they don't have assets, it's very difficult to collect on the judgement.If you are letting them stay rent free as a sort of charity, it's my opinion that there are much worth worthwhile charities to donate to. 

You can donate to local rent assistance programs.

I picked up extra shifts with the fire department, did odd jobs around town and even donated plasma to save up the capital I needed to make my next purchase.

They survive "donation to donation".

There is someone who will buy or pick up anything on Facebook Marketplace, anywhere, but if you don't want it you should donate it to someone who can put it to use, maybe a domestic violence shelter that needs to furnish apartments, etc.

that and potential donation write off in excess of their basis. 

Dont forget the political donations you may have to make to get things done . 10 plus lots , you are in competition with long time players .

Even $100 a month is still $1200 a year that could be going into your kids college fund or paying for great trips for you or you could donate to your favorite charity.