Long, straight, hair that is thinning and needs body - help!

Hi all! I have long, straight hair. Over the years, it has thinned a ton due to illness, many surgeries, and I went through menopause very young.

I wash my hair about once a week. Other than heat protectant spray, I don’t use any product in it because everything weighs it down or makes it oily too quickly.

I used rosemary oil for awhile but doing it just once a week didn’t really help anything.

I would love to get extensions for fullness but due to my health, it’s unaffordable. Even a haircut is unaffordable.

I was thinking of trying minoxidil in the future but not sure I could upkeep with the expense.

Anyway, my question is about adding body on a daily basis. Is there a way I could use Velcro rollers each night without washing my hair to produce body the next day? Or what else might help without me washing it?

Thank you for any advice you might have. I’ll also take any advice for the thinning, but doubt I can do much other than minoxidil.