Jamin,
The vendor has every right to say Net 0, net 10, Net whatever. The rules should really be yours, not theirs unless you agree to them ahead of time in your contract.
We simply state that payment is due at time of service. With a $10 late fee accruing for every 10 days the balance is overdue.
We have told commercials and HOA's from the get go, No check or check writer waiting for us no work plus a $200 service fee for showing up. Want us to show up again, 50% no-refund deposit. Make the same mistake twice Prepaid only.
Most of the slacker companies wont hire us and the quality ones have no problems with it. In fact, we end up relaxing for the quality ones.