I would get a Thinkpad, either used or new, with that budget. Generally all the hardware will work out of the box, with the possible exception of the fingerprint reader if it exists. RAM and SSD should be replaceable, so if you purchase new just do the upgrade yourself to save some bucks.
I don’t know how safe this is, but what I do:
Spend it where you can, not many places. BTCPay server, which can be self-hosted, supports it, so there are options.