Debit by itself is not a problem, it is debit to income ratio.

Seems like you are knocking him down pretty far, beating him up on normal prepaid items, and asking for a hand to do so. 

.:)Many of the charges you'll get from title attorneys are pre-paids (taxes and insurance).  

“Prepaid interest” is a thing: that means my first six months are paid and I don’t have to worry about paying for six months.

Yes it can come from the seller if the seller carries a note back, but the seller cant outright contribute proceeds towards your down payment ( closing costs and prepaid costs yes, but not DP).You'd need a lender who understands the lenders guidelines regarding a creation of a 2nd mortgage note carried back by a trust deed in CA.

Debit cash, credit experience

You can then cash out with NO seasoning, based on the new appraised value, up to the max LTV (owner occ 80% 1-unit, 75% for 2-4 unit, and investment property 75% for 1-unit, 70% for 2-4 unit), not to exceed your initial investment, plus closing costs and prepaids. 

I was thinking I could try having her use a deposit only debit card to directly deposit the rent every month at the bank (since she is already going there to get the rent money), but I'd be concerned about her depositing only partial rent.

You'll need certified funds to go to closing or a check if it's not much and acceptable to the settlement agent.There are no points on equity loans, points are pre-paid interest.

The debit service is the principal plus interest payments.