What does the guest require from you? Are they expecting the full breakfast and room cleaning everyday? Do they plan to use your kitchen for their dinner prep? Will they expect to use your washer and dryer? Will they think it’s ok to ‘invite a few friends over’?
Before you know what to charge, figure out what they expect, or what YOUR terms of engagement are.
Also, for monthly rentals, find out the laws in your area regarding who is a transient and who is a tenant. One pays lodging tax and has no rights. The other does not pay lodging tax and has rights of tenancy meaning if they refuse to leave you have to have them evicted.