You can probably call any local law office and ask. I'm 99% certain whoever answers the phone will hand you over to a law clerk who will give you the cliff notes version of what you'd need to know for free.

If there's a local university with a law program, you could probably send an email to a member of the faculty and probably get a response. You might also find a group on the university's website that specifically exists as free/low cost legal outreach to the local communty.

That should give you the specifics that you'd need to comply with for the local laws and such. If this affidavit is for something not directly requested by a court (like an insurance company asking for witness statements) ask your friend to ask whoever is requesting an affidavit for their criteria.

In general, make no assumptions or guesses. Don't speculate. Keep your answers and descriptions short and to the point. If you aren't sure about something either don't include or (if you MUST include it) specifically mention that you have little confidence in a particular statement you have included. Unless you hate your friend, anything unclear can potentially be used against them in their case.

You can usually just Google the state you're in and "affidavit form" and it'll come up with the little magic language you start and end with. It's usually like "on this day, _______, being over 18 years old and of sound mind did declare _________" and then it ends with "Further affiant sayeth not"

Affidavits sometimes need to be notarized. Some states allow for unsworn statements which don't need a notary, but can be used for most of the same purposes.

Hope this helps

Chatgpt. You may just have to word your request hypothetically.