If you stop paying rent then your landlord will start adding late fees and then usually after a few months of missed rent payments you'll get an eviction notice and be told to pay up the rent or you'll be evicted.
You can then leave the apartment or home at your own will when being evicted which is the best thing to do if you cannot pay the rent.
Or wait until the landlord takes you to court and then forces you out.
Just be aware that while a landlord legally has to take you to court to force you out of the rental place that it's not the best thing to happen to you.
Being evicted through court makes it harder for you to get a new place as some landlords won't want to rent to someone who has evictions on their record.
So the best thing to do is to pack up and leave before going to court.
Paying rent in cash is legal.
If you pay rent in cash just make sure you get a receipt for payment of rent.
Because without the receipt when you pay rent with cash there's no proof you paid the rent.
So always get a receipt when paying rent with cash.
I've paid rent with cash before and never had any issues as I always made sure to get a receipt in case something came up.
Other times I've paid rent with a check or money order.
But some landlords may only want cash for rent which okay.
If the landlord won't provide a receipt for the cash rent payment then I would look elsewhere for a place to rent.
Also always get a lease as well.
People have been paying rent in cash legally for a very long time.