The things that most often go wrong, from people who have been through them.
SELLING UNLIMITED
Your allocation is finite. Unlimited means the limit is discovered by everyone simultaneously, at the worst moment. Set real quotas.
COMPETING ON PRICE
The cheapest offer wins the clients who cause the most work and leave first. Compete on responsiveness instead.
NOT BILLING IN ADVANCE
Carrying unpaid client accounts while your own invoice falls due is how resellers get suspended, taking every client offline at once.
NO WRITTEN TERMS
Every dispute traces back to something nobody wrote down: backups, support scope, or what happens on exit.
NO RECORDS
Not knowing which account belongs to which client, or when a client's domain expires, causes avoidable outages.
NOT CHECKING DOMAIN EXPIRY
A lapsed client domain takes them offline and they will hold you responsible whether or not it was your job.
ASSUMING BACKUPS EXIST
Ours have finite retention. Take your own, off-server, and test one.
NO BUFFER ON YOUR OWN RENEWAL
If your reseller invoice suspends, every client suspends. Keep a margin and enable auto-renewal.