I've heard mixed reviews on it but we don't prefer to deal with Section 8 here, it's an arduous process.

Find one that can be custom to your needs, has flexible pricing, no long-term, high-cost memberships and excellent customer services to determine how to best market to your leads.

Which is also one of the 3 fundamental needs of a business most often (customers, product/service, place of operation). 

My suggestion would be to select someone with the most forum posts or most reviews.

Unless you have a specific monthly target for your payment you can spread that out to make it a Win/Win.There has been a lot of growth in Denver over the last 2-3 years and new builds as well I just closed on a home for a customer in commerce city they also moved from CA and needed a fresh start. 

Review the quality of the tenant base (do they have a history of paying on time, what were the original screening criteria, do they have applications on file).

I don't think the sellers agent does much. maybe take pictures and "review" the contract... the buyers agent is the one that shows the property and the one that draft the contract.

Marcus, the event was great and I truly appreciated your market review and forecast.

Their customer support is terrible and some of their software, but they have about 8x the site traffic in general than Airbnb and VRBO combined, surprisingly.  

Get a copy of the agreement and review every word of it.