My son had a chat with me tonight about his GF moving in. She has been sharing a place with her sister but they have been advised that when the lease expires in 2 weeks that the rent will go up by about 50%. GF's sister has already decided to move out and even if another co-tenant could be found  the new rent will be too high.

I know what GF is paying net now which is similar to the shared room rate for a single in a similar house in this suburb. But of course it won't be single occupancy here and she is unlikely to get rent assistance (she is receiving a youth allowance as her parents live in a country town and she is going to uni in Perth). On the upside having GF move in here means that I will see more of DS, his dog and cat will be much happier and food that is bought may actually be eaten.

But I'm struggling a bit on deciding how much board to charge. GF won't move in if I don't charge something but I'm also aware that this house is a lot lot further away from uni and her (part-time) work so definitely increased petrol for them.

Does anyone have any suggestions on what is a reasonable board amount to charge for two uni students?