Studio Design assistance needed - location/layout/budget

Hello, new member here. I'm currently in escrow on a house in Long Beach, CA, and I'm hoping to build a small studio on my property. I only discovered this forum a few weeks ago and just ordered Rod's book last week, so I've got a steep learning curve ahead of me but I'm still hoping to get as much planning out of the way as I can during escrow. I was originally planning to put the studio in the detached 2-car garage, but I just found out that would be an unpermitted conversion. :evil: Since I do not currently possess the political clout necessary to incorporate my plot as the City of Burgundia, shining metropolis of permit-free studio construction, I have decided to explore options for building an extension onto the back of the garage. I'm hoping the forum members can help me put together a basic layout that I can then take to the city for their input, at which time I would return to this forum with more details. According to the city building & planning office, this extension must be no more than 290 sq ft and less than 13 ft tall (I do have the option of making a vaulted or sloping roof). The south side of the garage is 24 ft long, and the back fence is approx 14 ft away (neighbor's yard backs up to opposite side of fence). The garage door is on the north side so no worries there, and the house itself is just a bit further north. The west side faces my grassy yard which is around 20 feet wide. The east side forms part of the property line with the other neighbors (again their yard backs up to fence on their side). The lots in my neighborhood are about 110 ft x 50 ft to give you an idea of how closely we are all packed in...I'm sure it seems like sardines to some of you! I've attached a PNG showing approximate dimensions. The light blue area is the proposed location for the studio. I've also attached a pic of the area. Since this is approx the size of a 1-car garage, I was hoping to adapt the Garage2 floorplan from this sticky. I am thinking that the control room would be on the west side and the live room would be on the east side? More info: the studio will be for personal use to record vocals (mostly ambient/operatic but some belting) and also some acoustic instruments like violin, piano (if it will fit!) and guitar. No drums. Hardly any street noise at all, given that the north side of the garage is over 60 ft from the quiet residential street. No dogs in adjacent properties (and hopefully will stay that way). There is some flight noise from the airport (about a mile southeast), and I am on the departure side although the planes turn south immediately after taking off so it could be worse! Unfortunately I haven't had a chance to measure how loud yet; it was enough that the previous owner installed double pane windows in the bedrooms yet not in the kitchen or living room. My questions are: (1) Is adapting the Garage2 floorplan doable in this space? (The original plan is dimensionless so I can't tell for sure how well it scales.) If not I'd appreciate suggestions for a better layout. (2) Approx how cheaply can I do this, given that I have no background in construction and would probably be hiring a contractor for most if not all of it? (I'm hoping to do room-within-a-room.) I understand this is an obscenely general question but I just want a ballpark: if you've never seen something like this built from the ground up for less than $30K then I won't even bother calling contractors to get bids. Originally I had set aside $8K, but I can go up to $12K if needed (and maybe squeeze out a bit more as the months go by). I am mainly concerned with functionality, I don't really care how "pretty" the outside or inside looks as long as it passes inspection. (One caveat: the outside will have to be stucco just like the garage). I have a separate equipment budget so this money would be strictly for construction.