First you will need to know if this is inside your townhouse and if it is allowed. Then where will you put it since you can’t touch the exterior of most town homes

Are you doing a gut reno or looking to add one in a home ther is move in ready but you want to add an elevator?

you would need to find out if the HOA’s allow them & whether or not there’s an appropriate space for it. Elevators are commonly included in many new builds in my town ( beach , So Cal ). I’ve also seen them offered in two level condos in Palm Desert.

And also, when you say townhomes in a major city, it can mean a LOT of different things to different people. It can mean huge tract development “townhomes” that are builder basic in Los Angeles or Atlanta, it can mean brick rowhomes in old town Arlington or Georgetown dc, it can mean 15MM townhomes or brownstones in Brooklyn or Greenwich village. Or rowhomes in Chicago

I would look for one that comes with an operator who can ask you what floor you want and tell short jokes during the ride.

Would a chair style lift work for you? Much less invasive installation than an elevator. They even make some able to raise a wheelchair.

https://butlermobility.com/