Power, Domain Name (if using a standard paid one instead of the cheaper route), VPN are the 3 that I pay for that I feel are the bare minimum.
I pay for a domain that's $12, but you could easily get the $1 ones for the same purposes. I pay for a static and service VPN with Windscribe, which comes out to be like $35+$89 respectively. So that's already $136 a year excluding the cost of power. I could cut that cost easily, but I use them for more than just my selfhosting so I feel like it's a fair price for what I get out of it.