Estimating size has always been tricky, because it depends on the insulation value of the boat, climate, and how quick you want the boat to cool down. It also depends on window covers and awnings and how much window space you have. Houses, on the other hand, tend to have similar insulation values, and the rate at which they cool is not important because people leave the AC on all summer.
If you're going to sail you'll be doing some stitching-no two ways about it. That doesn't mean you have to go overboard with sail repair tools. Don't jump into the $100 do-everything kit. Start with a modest kit, adding tools and materials only as your skills grow and projects require them. Chances are, you already have most of what you need in your other supply lockers or tool boxes.