I am thinking to say money
Did you want to write: I am thinking to save money... ?
What you have in mind is certainly feasible. But it is not the cheapest version. The power consumption (24h x 365 days) of an old PC is more expensive (200%?) than a small hosting package (and you will not need more) of a provider. And the provider certainly offers higher availability than a single PC at your home.
Just my 2 cents - Michael Sy.