How do we enter real estate rental income on a monthly basis?

Hi @cuhlik83,

You can set up the rental property as a Customer and the tenant(s) as a sub-customer(s).

Here's how to add a sub-customer:

1. Hover to the Sales tab, then select Customers.
2. Press the New customer button.
3. Fill in the Customer information form as necessary, and don't forget to put a check on the Is sub-customer checkbox. 
4. Select the parent customer (the rental property) for this sub-customer. 
5. Click Save.

You can then proceed with invoicing the tenants every month. 

Also, since this is monthly rent, you can consider creating the invoices as a recurring transaction. Check out this article for details: How to create a recurring invoice and manage recurring transactions.

Feel free to leave a comment below if you have additional queries, I'll be sure to get back to you.