Be the Guarantee, Not the Introduction.

If all you do is point the buyer at a supplier, you've sold something they only need once, and they'll never need you again. But if you stand behind the work - if your name is on the outcome, if you fix it when it breaks, if you carry the risk - then you are not an introduction, you are the safety net. And people pay for safety nets forever.

The guarantee is what makes you permanent. It's the reason a customer keeps coming back to you instead of going direct: not because they can't find a supplier, but because they don't want to carry the risk of the supplier failing. You carry it. That is the job, and it's the difference between a one-time finder's fee and a lifetime customer.