Avail recently got bought by Realtor.com and Avail has live customer support every time I have a question.

For a low-cost solution, you can create a simple Google form with custom questions and share the link with them.

Keyrenter North Jersey opened this year, leveraging the proven processes, systems, technology, and infrastructure of the large organization, combined with the focus, support, customer service and local expertise of a small business.

We're spending ~$300k and it's completely custom.

Honomobo offers very limited customizations of their products which consisted of models numbered 2 through 5, which corresponded to the number of 40x8x9.5 shipping containers that they used.

Experience will matter to some of customers, so you'll have to be specific about your history and success. 

I'm an experienced investor, agent, and a project manager for an established general contractor, focused mostly on historic preservation, custom homes, and investment properties (flips and holds). 

I just closed one for a customer.

BTW, Avail's customer support is US-based and fantastic. 

If you could customize the software that you are using, what would you like implemented?