I do run my own mail server from home, I have a second MX proxy on AWS, so even if my home goes out for a bit (less than 3 days) it will mail will be collected on my AWS server.

Getting it setup is easy, and cheap.

But getting it set up right is not, make a mistake and you could be an SMTP relay, people may start sending out bogus mail on using your email, and then there is the maintenance (backups, patching, etc)

Even if you were able to purchase a block of class C, who know what the reputation was prior to that. Then you need an ISP that will route said IPs to your home.

I have a small block of IPs (/29) and I think I pay 3 times what my residential peers pay.

I self hosted Exchange 5.5 at home, then went to SBS 2003, then SBS 20008, after that moved things to Hosted Exchange.

I still host a local mail server but it is Postfix and Dovecut (prior to Exchange 5.5 it was sendmail and uw-imap). My IPs are closing in on 2 decades old, and my domains 25 years.

If you want cheap and able to wait, maybe put it on AWS with an EIP, and wait till it is eventually clean. Be aware that if you get an IP from AWS even if you dont use it you will be charged and you still have to have them allow port 25. There is their SES service, but now I feeling you getting away from r/self-hosted.

New just established domains get a low reputation as well.

I encourage people to learn though, ask more questions here, expect most people to say don't do it.

Good luck