Garage workshop feasibility questions

Mazeroth

I have a 20w x 24d garage that's a little too cramped for my liking. I would like to add an addition onto the back of the garage the same 20w and probably 16 deep. Right now my garage is used for parking my wife's car as well as my weight lifting equipment and general storage. We have a very small ranch; so small that my computer desk is in the basement next to the furnace! The addition I add I would like to have a poured concrete floor, very well insulated (unlike my current garage) and heated and cooled via a mini split that will run off 120v 20A. I'll put all my weight equipment back there, my computer, and anything else that will make it a comfy spot for me to get away from the wife and kids and do my thing.

I'm a very handy guy, having completely gutted and remodeled our entire house. Taking out walls, redoing 2 bathrooms, installing hardwood floors, kitchen cabinets, and putting on 25 squares of shingles. I did have a framer help me with the framing and I know a drywaller so I didn't touch that stuff. I would be paying for someone to pour the slab, to do all the framing (tie new roof into old as well), siding and my buddy to do the drywall. I will do the electrical, insulation and roofing. Ok, now onto my questions.

This is a feasibility e-mail and a wakeup call I'm looking for. We only have 0.25 acres so a detached is not an option. If you look at the pictures below you will get a pretty good idea of what I'm working with. Please excuse the mess on the back patio as I've been super busy with work and remodeling to care about cleaning that up! My main concerns are tying this new addition into the existing garage. My current garage has 10' ceilings. I would be fine with 8-8.5' ceilings in the addition so that I can tie the existing roof into this one. I will not be able to keep the same roof pitch to maintain my desired ceiling height. Will this be a problem?

The main problem areas are where the garage attaches to the house. Is this going to be an issue where the house soffit overhangs a little bit, or will the framers have no problem fixing this?

Also, on the left where the garage gutter goes down into the current slab (that slab will be taken out), I don't think it's going to be a major issue extending the gutter drain back 16 feet and tying into the new gutter. Thoughts?

For the siding on the left, will I need to take some pieces out for the new siding to tie in so it will look like one long wall, or will I be able to leave that 90 degree piece in there?

Any other glaring faults in this plan? I'm hoping to keep the total cost under $10,000. Crazy?

Thanks!

madmax

Seems like it would be hard to keep enough angle on the roof if you brought it out 16' without raising the overall garage height several feet. (I'm not a builder, don't even play one on the internet)