How to give money?

I will be staying with a host family for a couple of weeks and have already paid my deposit online.

When I actually meet the host family, I need to pay the rest of the fee. I'm just wondering how to do it?

Do I have to put it in a special envelope or something like that? What if the notes I have aren't as crisp or clean?

Also, what value of a gift is appropriate to give, and do I give it when I meet them, or after they stay is finished.

Any help is much appreciated, thanks.

A regular envelope is fine, and don't worry about the bills.

Give the gift when you first meet them.

just buy food or fruits and give it after you buy it so it's fresh.