Onboarding a new vendor

[Jon K.]

A friend of mine in Maryland is starting a GC business and has a deep roster of subs. He wants to focus on large ticket items for property managers: roofs, turns, hvac replacement, whole house painting, things like that. He asked for my help or advice in how to get onboarded as a vendor for professional property managers so I thought I'd ask here. I know most PMs already have go-to contractors for most things but I also know from experience that good contractors tend to get busy or scale to a point where quality suffers.

For the professional property managers of the world, how often do you get solicited by new vendors and what can a new one do to convince you to give them a chance? For what it's worth he's a landlord himself (19 units) so he understands the business pretty well.