You can find them on any witchcraft forum, group, or board.
You won’t be charged money for them, but there will be a price.
If someone is offering spell casting services for “free”, it is to obligate you to them spiritually or to extort you.
If it is about a spiritual obligation, they will get one of their helpers to seemingly solve your problem, but then you will owe them. They will then use your energy for whatever they want. I’ve encountered a few people who got a “favor” done for them by someone they met online or who graciously answered their call for help in a witchcraft group, and are now basically enslaved.
In order to be freed, they ended up having to do offerings to the deities they should have gone to for help in the first place. Sometimes, especially when dealing with love work, some people are so busy trying to get a bargain or to take advantage, that they are cheap with their own ancestors. Yup…sometimes if they had just taken a moment to give some offerings to their ancestors once a month, their love life wouldn’t have been in shambles in the first place.
Some people offer “free” spells as a part of an identity theft or extortion scam. They take advantage of the need to give one’s full name and birthdate and photos, and use that to threaten people. They sometimes threaten to tell the “target” of the spell what the one who asked for the spell is up to.
At least if you pay someone for work, there is a paper trail or transaction record. So if they try to harm you, then you can take that information to the authorities. If it’s “free” you have no idea who you’re dealing with.