Got my taxes done yesterday

[Old Crank]

4. Renting a room.

Yes it is income.
It also opens up a whole new can or worms when you rent out part of your house.
On one hand it allows you to claim a portion of your house as a business expense. That means that you can deduct expenses related to that and you might have to depreciate that part of the house also. So you mgiht actually lose money on paper while renting out the room. This can be a problem when/if you sell the home as the profit from the sale of the depreciated asset would be taxable.... Fun stuff to deal with for say 20% of your house.
I wouldn't declare the income if it was a low amount. The cost v benefit is too much if you do all the corerect accounting.

As for helping others do taxes, in CA if you get paid you need to be registered with the IRS and the state tax people. As a volunteer you may not need to do so where ever you live. But make sure that the volunteer group has insurance that will cover you if a mistake is made and someone wants to claim damages.

I did my own for many years and got the federal certification.

These days I pay ein Steuerberater für meinen Einkommen.

The biggest rule to follow is: RTF or RTFF. Read the (f'ing) form. and FtD, follow the directions.
Back when I did it, Publication 19 was your friend. That covers virtually all an idividual needs and a lot more.
I think it is only on line now.

Best of luck.