Why it's a bad idea
Risks
Meta's rules
Meta's Advertising Standards prohibit selling, renting, buying or exchanging administrative access to assets.
You don't own it
Whoever sold it still may hold access, and can remove you.
It can be shut down
Restrictions on the old account can follow you, and Meta won't refund spend lost.
What to do instead
1
Create your own ad account inside your Business Portfolio
It takes a few minutes and you own it from day one.
2
Set up business verification
Meta may require it before ads run at all.
3
Add payment and a verified domain
Needed before your ads can run reliably.
4
Warm up, don't rush
Start with a modest budget and increase it gradually. See scaling budget safely.
Already bought one? Check who actually has Full access in Business settings, People. If the seller is still there, that is a problem to fix before spending anything.