How is the demand for rental properties in Carlsbad?

Also, I just got my real estate license and I want to sell/buy homes on the side considering it is a hard time to find deals and I have a fairly demanding W-2 job. 

That said, its also likely that you are in a life position to tackle repairs and such yourself, reducing your need for as large a cash buffer as someone with a career demanding 50+ hour weeks.It might be wise to wait until you have begun your career, have a strong savings rate, and THEN house-hack.

Day one cash flow is not the same as cash flow 10 years from now ... you need to make sure it is increasing on an inflation adjusted basis and that goes to the quality and long term supply & demand fundamentals of the neighborhood (hint: quality neighborhoods don't cash flow as well day 1, but do better +10 years).

I wouldn't demand the single payment system from my tenants.

My first broker demanded that I pay her a commission split on a property that I bought personally that was for sale by owner.  

But they are establishing the nature of the relationship by making demands of you, pulling your into lease negotiations, and not paying the lease. 

Is there a good demand for rentals in the lake Stevens, Everett area?

Keep looking at all the listings and also rentals so you start getting a feel of supply and demand and asking price.

In addition, they (her agent and seller's agent) keep pushing her to sign for "Demand to Close" form, while the seller doesn't finish replacing the roof yet.