Congratulations on your purchase! I've been doing this for about a year and a half, and I have an 8-plex. Here is what I have learned:
Communication: I have a Google Voice number that is directed into my cell number. I have it go straight to voicemail. If tenants or other call they will hear: "Thanks for calling Hardwick Place. We currently are full, but please lease a message if you have any questions. Thank you!" It works great, especially since most of the calls are telemarketers. Tenants usually correspond with me through texting, which is great because it makes a record. You can use Google Voice on your computer to make texting faster too. They send notifications to my email when I have a voicemail or text.
Payments: I have a drop slot in a door under the stairs. They can also pay through my Quickbooks via ACH, or just deposit it straight into my bank.
Addendums: I have found a lot of great paperwork right here on BP and have modified it to suit my needs and my laws.
Relationships: Like you said, treat it like a business! Be nice and friendly, but don't make friends. Don't stand around and chat a lot. I made that mistake and am paying for it. I spent a lot of time in the summer of 2017 remodeling 2 units in my building. One of the neighbor ladies across the hall would come a chat or bring me her baked goods. We got to be friends. A year ago she lost her job, and her husband can't work, so she got behind because I couldn't make myself evict her. Now she's slowly paying my back extra every month. It really affects my financials though. When someone doesn't pay rent it looks like I have an empty unit. That affects my property and resale value.
Don't be someone's bank! if they lose their job and can't pay their rent, that's their problem to solve. They can borrow from friends, relatives, the bank, etc. It's not your job to "borrow" them money by not making them pay rent.
Good luck! :)