I've now learned that this is because so few respectable vendors will work with them after not being paid for jobs that the ones who will work with them are not necessarily the A squad.. 

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.

What resources / vendors exist out there for this?

Hey @Devin Bost, I would highly recommend a few things to help with this. 1) Have systems and processes lined out for any emergency you can think of.2) A spreadsheet of subcontractors/ vendors that could handle the situation that arises (plumbing leak, electric out somewhere, etc.)3) Your cleaning team and handy person should be utilized for some things.4) Something like Breezeway can give you 24/7 support around your property with a dedicated phone number line.

The inspection is a 5-10 minute walkthrough by a vendor who will take pictures of every room and identify any issues for you to address.If there are issues, you typically have a week or two to get them fixed without there being an impact to you.

Keep in mind any premises liability, landlord tenant, contractual dispute with a vendor that performs services in CA will be  resolved in CA if that's where the real estate is owned and operated. 

Construction documentation, such as construction drawings, specifications, contracts, job reports, change orders, payment requests, and vendor and supplier invoices, are used to determine unit costs.

Also, I want to create an in-house store with Stayfi and The Host Co to sell themed merchandise and local vendor services.

Perform the same task in each app to ensure a fair comparison.Load a property with pictures and details.Market that property.See what your marketing looks like from the public's perspective.Submit a fake application to see how easy the process is.Run a credit/screening report on yourself.Enter a maintenance request, assign a vendor, and attach a fake invoice.Enter charges to the tenant's ledger.Enter recurring charges and automatic late fees.Sign documents electronically.Run owner reports.After testing a few apps, one should clearly stand out.

Treat it as you would a processing error from a valued vendor and u are in a good spot.