Let's be honest here, almost every proxy you get, even from a reputable, dedicated runescape proxy seller has been used before by someone else. It makes no commercial sense to purchase IP's costing .5- 2$ / month, rent them out for a while and them discard them
Why? Because IPv4's are scarse, server providers no longer throw them around and you can't just ask your provider to swap out an IP to a fresh one.
Selling an IP to multiple users simultaneously is a different story, that's where 'premium' proxies make a difference.
@OP:
If you're doing F2P, rent a single proxy somewhere and run all your bots in different worlds on the same IP, it will pay itself off in a day or so with 4 accounts. Then you can think of buying more Your mule can safely stay on your home IP