What is the right way to ask

A renter rents 'from' a landlord. I rent my apartment from Mr. Biggs.

A landlord rents 'to' a renter. I rented [leased] 210 Elm St. to Mary J.

An apartment that is on the market to be rented is 'for' rent. 201 Elm St. is for rent.

X rents Y - X is staying at Y and paying rent to the owner of Y (X is the tenant).

X rents out Y [to Z] - X owns Y and is letting Z stay there if Z pays rent (Z is the tenant).

X rents Y to Z - Same as X rents out Y to Z.

X is for rent - The owner of X is looking for a tenant.

X is renting [out Y] for Z - The owner of X is looking for a tenant that will pay Z if Z is a cost, or the owner of X is seeking a tenant on behalf of Z if Z is person. Y would be the place itself if specified.

If you want to let your friend stay somewhere in exchange for money, you are renting or renting out a place to him.

If you are asking what would be an acceptable wording for a statement offering an apartment for rent, here is my suggestion:

"I have an apartment for rent. Are you interested?"

Or if the statement will be used for an online or written advertisement, I suggest simply: "Apartment for rent:" followed by the terms of rental, such as the amount of the rental fee, whether or not utilities are included, and the size of the apartment and number of bedrooms/bathrooms.

As for your question regarding whether you can offer a friend an apartment that you have for rent, whether or not it is appropriate depends entirely on the situation and what your friendship is like. I would say that if you have an apartment for rent and you have a friend that is looking for an apartment, it is usually appropriate to simply notify that friend in a statement similar to the one I suggested above.