I disabled the option to pay via credit card because the fees seem too steep for a tenant to ever consider doing that. 

I’ve been watching the West Haven market from Florida via the MLS, as I would like to buy and house jack.

It's those maniacs that buy homes cash via quit claim deed off of craigslist that really get screwed.Make sure your property manager is a licensed real estate brokerage.Google Clayton Morris scam and/or Morris Invest scam for a cautionary tale of what not to do when buying turnkey real estateUnderstand you can not eliminate all risk, only mitigate it.

Any suggestions from landlords on the best app or tool to accept/process monthly rent payments via credit cards from tenants? 

I prefer to send that checklist to them via email to let them know this is what I am look at, but I also walk through WITH them before they move out, so we can talk about what will likely be held back from security deposit, and allow them to address it beforehand. 

I used to have a credit score in the 760s but I bought a distressed property and used credit cards to rehab it, causing my credit score to drop to around the 600-620s, but my plan was to do a cash out refi on 5/1/2020 (that'll be 6 months since I bought the property via hard money) so I can pay off the debts.Is there anyone who can lend 30 year fixed conventional investment loan with lower credit?

The rest would be financed via private or mortgage.

In my opinion if you are going to block income, you should block ALL expenses associated with the property as well (even though nothing should be blocked to begin with).New York is a classic example of big brother over stepping it's boundaries in a really problematic way. 

We offered a reduced price via closing costs credits, and additional favorable stipulations.

The increased risk of being unable to service debt can be observed via the downgrading of the "credit ratings" of many corporations by Standard & Poor's, Moody's and Fitch.