This is very similar to the situation that I had last summer. Same era and type of houses. My neighbors (whose garage was only 1 foot from the shared property line, and only 12 feet from my house) wanted to build a 2nd story onto the garage, and extend the structure both in front and in back (which would have brought the rear corner to within just a few inches of the line since their house did not sit square on the property). I had also had some difficulty with them because of trash issues but tried not to let that influence my feelings about the addition. So, I also was concerned about the loss of light and having a view of only the side of their house rom the dining, living and 2 bedrooms (they are close now, but with the garage placement I do get light and see sky and trees). I wasn't sure it would be putting that side of the house in constant shade, but it seemed like it would and I was concerned. This neighbor told me that I shouldn't care because in another, newer suburb, the houses were all constructed like that (which could be why I don't live in that suburb). . I wrote a letter to the board in charge of the zoning variance permit and simply told them why I was concerned. I did not come out and say that I was opposed but had these concerns. The board did take that as an objection and had quite a discussion at the meeting (I read the minutes later). One board member pointed out that although they may think that they will be there a long time, they possibly won't but the changes would affect my house forever and perhaps my home's marketability. They did not approve the variance, the neighbor blamed me, but he chose to sell in order to get the bigger house that they needed. Turns out though, that the addition would have violated state fire code (too close to the property line) and could not have been approved anyway. I have very nice neighbors now, very glad that I didn't have to find out if my fears were founded or not. You have more room between your houses; I wonder if there is a way to figure out if the proposed addition would block much light?

The average sq. ft. for a 2 car garage ranges from 19x20' to 22x26', depending on how much storage/utilities people want to set up in the garage. In our county, the minimum length for a garage is 18' (one car) with a 9' width. Hopefully this info can get you started, at least. My advice to you is to do the foundation for as large an addition as you can. Use this opportunity to reconfigure your rooms next to the addition, if necessary. You are looking for a good "flow" between the old and new. Smaller additions actually cost much more per sq. ft. because all the same equipment is used, regardless of how big or small the addition is, when you are talking about foundations, framing, etc. Good luck! Keep us posted on your progress.

Good advice. I'd add beware of remodeling fatigue. It's not today's guys' fault the previous trades took so long. Don't take it out on him, please.

My 2 cents... I would not do it with an attached garage... You are just going to be overbuilding the garage and wasting money when you build the house. In other words, the cost of building an attached garage with a house will be significantly less than the cost of building a garage and later attaching a house to it. Aside from the cladding, you also have mechanical and electrical systems that you are going to plan and install with the ADU and that are largely going to have to be redone. The rentals that you get over the next seven years probably will not even cover the marginal cost. ---- This is a little different if you are doing a detached or semi-detached garage. However, you are still going to be overbuilding the garage to make this an efficient idea. You are going to have to plan where your plumbing will enter the house when completed. If you are on a septic system you should plan and/or install the entire system now, etc. Having a livable space on site while you construct a home can help with expenses, but having a ADU that you are renting to alleviate some of the cost is probably not as effective. Good luck.