Quote from @Jake Baker: @Tony MuratoreAccepting rent through payment processors like Venmo, Cash App, Chime, and Zelle can complicate the bookkeeping. 

A simple checkpoint I use is does the deal still hit a 1.25 DSCR at the refi under stressed rates and a higher exit cap, and is there enough reserves to survive the gap if not.Did they disclose the exact loan terms like LTV, IO period, extensions, and whether there was a rate cap in place, and what DSCR did it underwrite to at maturity day one?

Pros and cons with each lender that have to be weighed:  Rate, prepayment, amortization or IO, closing costs, and reserve requirements.If you decide to refinance, I'd recommend seeking out credit union quotes before committing to an agency deal and weigh those options against each other.   

How you organize it (app, spreadsheet, paper, memory?)

Quote from @Robert Leitner: I have a couple properties and use Stessa as my property management app but they don’t yet have maintenance and issue tracking.

Quote from @Purva Raichura: You’re right: serious developers don’t replace pre-app meetings, civils, or title services with software.

Then, you can find an app that will take the data and allow you to categorize the expenses.

Some common names you'll see thrown around a lot: Stessa, Apartments.com, RentRedi, TenantCloud, Innago, RentManager, Avail, Rentec Direct, Doorloop, etc.I recommend you search for each of those apps online and see what they offer, how much they charge, etc.

I'm just looking for a good app that can help me record receipts and expenses, help me management income. 

Communication is EverythingAmerican Airlines had to keep passengers updated through apps and alerts, reminding customers to check statuses frequently.