Learn Portuguese (Portugal): Eles arrendam a casa.

In Portuguese, there are two verbs for "to rent" depending on what is being rented. You use arrendar for real estate, like a house (a casa) or an apartment. You use alugar for movable objects, like a car or a bicycle.

How do I pronounce the -am at the end of arrendam?

Even though it is spelled with an 'm', the -am ending on Portuguese verbs is a nasal sound. It is pronounced very similarly to the -ão sound. You do not close your lips to make an English 'm' sound at the end!

If a mixed group of men and women are renting the house, do we still use eles?

Yes. The pronoun eles translates to "they" for a group of men, or a mixed group of men and women. You only use the feminine version, elas, if every single person in the group is female.