When you pay rent, arenyou paying for last month or for current stay?

Usually, at the start of each month, you pay for all of that month. You're right; she's wrong.

No, you are paying for the upcoming month. She is entirely wrong. She pays when you tell her she pays.

Its like your mortgage payment. You pay for the month coming up, so rent is due on the 1st of March to cover staying in the house for March, for example.

You always pay for the month ahead. Most commonly, rent is due on or before the 1st of the current month. You can make April rent due on April 3rd, and on the 3rd of any subsequent months, if you want to, but I do NOT recommend that. Make it the 1st. Your state law dictates the time frames and procedures for issuing demand notices for late rent, and eviction for non-payment. These time periods just add more time, time in which you are losing money if the rent isn't paid. So why put yourself three days in the hole at the start? Rent is due on the 1st.

She thinks you want your money too early? She sees you as a pushover, a weakling. If you allow it, you will have nothing but problems with her. YOU own the place, YOU make the rules, SHE can live somewhere else if the doesn't like them.

A tenant who pays rent pays it in advance ( benefits that pay the tenants rent send payments in arrears)

So a tenant who starts to rent, moves in on 20th, pays deposit and 1st months rent, which takes them up to 20 of the next month........ although some countries rent day is always from the 1st of the month...so if the tenant moved in on 20, they are likely to pay deposit and 1 months rent plus days from 20 to month end before move in date, although this should all be in writing in their tenancy contract

Rent is paid in advance. What she pays on April 1st is rent for the month of April (or however long the rental period is)

She should have paid for the first month the day she moved in, because rent is paid in advance. She should have paid you for March 20 to April 20 already, plus a security deposit. On April 20, she pays rent that goes to May 20, and so on. When you pay your mortgage is not relevant to the situation. You'd better get the agreement in writing, because this is already headed for trouble, as I see it. Ask for the rent money TODAY, dear, or you just may never see any of it. People will take advantage of your kindness if you let them.

Rent should be due on the FIRST of each and every month, regardless of when she moved in. Further, you should be charging her on a per diem basis from the 20th through the 31st of March, but since you gifted her with that rent, it is too late now. When your mortgage payment is due is totally irrelevant, as is the day she moved in. Why didn't you learn "how" to rent a room before you actually rented it? Did you get first and last month's rent and a security deposit? No? Learning through trial and error could be costly. I would not take my house for granted like you are. Present her with a lease to sign. If she refuses, evict her. Do it right so that you have recourse in court if you have to sue the tenant or if you are sued. If you are sued, you are screwed, when it becomes clear that you have no idea what you are doing.

Rent is always paid in advance.

If she moved in on March 20th and does not pay you until April 3rd and you aren't expecting back rent, then you've given her 14 days of free rent (3/20-4/3).

Her payment on April 3rd covers April 3rd through May 2nd, and the next payment is due on May 3rd (which would cover May 3rd-June 2nd and so on). You're always paying at the beginning of the rental period for the upcoming time period.

There's another important principle here - your house your rules. She is living in your house, she pays the rent YOU specify on the date YOU specify that it is due. She is already signifying that she isn't going to respect your authority as the owner and landlord, and that should be a huge red flag.

Also, don't compare paying rent to paying a mortgage. Rent is paying for the privilege of using someone else's house. If you don't pay, you immediately lose the privilege of using what doesn't belong to you. But with a mortgage you own the house, you have a natural right to live there and use it because you own it. You are NOT renting the house from the bank. You are repaying the bank the money they loaned you toward the purchase. The mortgage payment isn't come before or after the month because you aren't buying the right to live in your own home. You're simply covering accrued interest and knocking a little bit off your loan balance.

Typical rental agreements are paid in advance as a security deposit for damages, and first rental period of normally one month. Some agreements require the final month paid in advance as well, but that is for less trusted tenants. You therefore are paying for current stay, as rent is due at the beginning of the month for the current upcoming month and not in arrears like most hotels.

When the owner is paying mortgage is not relevant because that is a secured loan paid generally in arrears on the current balance and additional principal payoff.

You had a right to prorate March and collect 1+ 1 + 1/3 months rent as approximate.

You should have collected 2.333 times one month, as damages deposit and March and April before move-in.

You made the mistake of allowing an idiot cheap insulting friend to move in.

To have payment due on the 20th, she should have paid one month on March 20 as she moved in, and second month due April 20th.

You explain it to her by saying if you do not get immediate payment, you begin eviction as a house guest there less than 30 days without contract, so she has 24 hours to vacate or call the police.

You are both poorly educated in finance and legal matters.

You can be nice and collect less if you wish instead.