Give the neighbors your card and invite them to call you directly ("don't waste your time on these people, call me"). 

Others will disagree but I am not a fan of pulling the lawyer card w/ college students unless it is 1,000% necessary.

What cards are you using?

Hey guys, I have a potential renter wanting to use a credit card to pay rent.

I'm from RI and its legal to use medicinally, but as a landlord, I would personally prohibit everything that pertains to marijuana besides the consumption and possession if the tenant possessed a legitimate medical marijuana card and was within the legal possession limit. 

At the same time, though, it's all built on a house of cards/credit.  

If the deal is good even with borrowing the funds, then go for it.Refinance your house.Home equity line on your house.Sell something expensive (even your house if the deal is good enough)Put it on the Credit Card (works wonders, IF you're sure of your numbers:)Call everyone in your phone contacts and tell them you have a $50,000 opportunity you'd like to tell them about.Ask everyone in your contacts who they would be talking to if they had a $50,000 opportunity.Put a post on facebook or your social sphere of choice that you have a $50,000 opportunity for the right person.Call several local Realtors, specifically ones that do investments and commercial and ask hem if they're interested in a $50,000 opportunity and ask them who might be.Borrow against other investments like stock or borrow from your 401kBorrow from another investors 401k, your Mom's, your neighbors. 

Now that some of the cards are falling into place to invest in our first BRRRR here in the Houston Area, I've thought about approaching him for funds once I get everything lined up. 2 part question: What is a good interest rate to approach him with, and what is the best means to make this happen to protect both parties?

The downside is tenants have to pay online whether it's through ACH or credit/debit card; no money orders or cash.If you let the tenants pay by cash make sure you are protecting yourself. 

Have business cards that say you buy houses & plexes.