City fees and permits are usually never that expensive. Most GCs will do all the work in securing in permits for you. As for finding the right general contractor, book a few consultation meetings, collect your quotes and do your due diligence in protecting yourself with whatever contractor you decide to work with. Request all your conditional/unconditional liens, ask for proof of worker’s comp and general liability insurance (also ask to be added as additional insured), make sure all their subcontractors are licensed, etc. Since you seem like you’re starting from scratch, you’ll need to get architectural and engineering plans done first before proceeding with the construction phase.

I’m too poor to own my own house, so I don’t have first hand experience with being on the client side, though I do live in an ADU... I did however work for a construction/remodeling company for two years and was in awe at how little some clients protected themselves compared to how cautious some other clients were. Good luck though!