Because we are within the coastal area, my architect is saying that I need to pay an $18,000 application fee to the coastal commission and the waiting time to be approved is 6-9 months.  

Demand evidence to back up the charges or threaten to file a lawsuit or a complaint with the state.If they don't respond to your satisfaction, file a complaint with the state licensing commission.

As an agent - my real estate business - I ask for a certain commission based partially on how easy a client will be to work with.

That's right, getting a commission out of the $20,000.00 they just snookered you out of (probably 50%).

My understanding is: most sellers will pay their commission, but what if they don’t or they only pay a portion of it?

In fact, Bank on Yourself professionals make 50-70% less commission than other insurance agents so that these policies can be more productive for the client.

Does anyone have any knowledge on whether I can represent myself in a transaction with a builder on the purchase of a new construction home for myself as an actively licensed broker in WA Seattle area and collect or save on the commission myself?  

I mean once you talk to them, it's pretty easy to spot if they know what they are talking about.I've work on STRs before and to be honest, it is not the most fun aspect of accounting because the volume of allocating income from all sources (airbnb, vrbo, stripe, direct booking, and so on) to a bunch of random expenses (cleaning, supplies, repairs, advertising, commissions, and all typical real estate expenses).I had to strictly rely on the client's input on what the expenses belong to which property or even units, if the paperwork doesn't say. 

Is property management regulated by the real estate commission in CO? 

I am very data driven and I simply don't see Philly as an attractive destination unless you are -- local, hands on, DIY, don't have prop mgmt expenses, don't pay leasing commissions, get preferred rates from lenders, know a guy who does handyman work, etc.