There are a few ways you can collect rent. Starting out with your first rental allows you more flexibility, the more units you scale it would be wise to have a more thorough and consistent process.
Cash: Most people will advise against cash because it's hard to track and inconvenient. 11% of American's don't have bank accounts though, sometimes this might be your only option. If so, create a receipt for EVERY transaction that both parties sign. Be smart and safe when you pick up cash too.
Bank Deposit: There are tenants who will make a direct deposit into the landlords bank account. You will need to provide them the bank and your account number. This does create a receipt which is nice and avoids the face-to-face interaction.
Apps: When you only have a couple of units you can get away with using apps and multiple sources. Zelle, Venmo, PayPal all allow you to be paid electronically. I typically advise you to pick whichever the tenants prefer, make collecting rent easy! Again, this works when you only have a couple of units to check.
Rent Collection Sites: There are several management software sites like Burbz, Cozy, Tenant Cloud, Turbo Tenant that have integrated rent collection. They work exactly like the apps. Some sites are free and others charge. The positive utilizing one of these websites is it allows you to scale your portfolio on a single platform. Plus there are additional features you can access for free to help make managing easier.
Let me know if you have any questions! Best of luck!