Moving, going to need to build a garage

Bad Sport said
Balance your budget against your wants.

If I were doing it, I would consider what material to build with, in your climate condensation might be an issue. For example, a tin roof as opposed to wood/shingles etc.

Heat? Air conditioning? Bathroom/shower maybe? Lighting would be one item at the top of the list for me, type of lighting for good light and cost effective.

Lots of electrical outlets all around.

64DartGTinAZ said
Make it as big as your budget will allow - way easier to add things (like 220, more outlets) later, than it is to add more square footage.

Both of these have good suggestions. I would also say shop around extensively for the materials. I'm looking for one now myself, and I can say this, the complete, easy kits often cost more than just buying the materials individually. Example, I'm looking at a kit now from one, 24 by 32 ft and it's list price is 5976.96. Well, I added it up individually, I can design and build my own, for 3967.36

Also, in terms of concrete, get the strongest PSI tensile strength rating you can in your area. Especially if you're gonna add a lift.