A large space concept is looking for ideas

I had an apartment in the basement for years. Yes, there were definitely surprises. Neighbor's cat, raccoon and co. I have no problem with the four-legged ones, insects (yuck) are just as many upstairs as down. But it was nicely cool

I slept on the ground floor for a few years and actually had visits from hedgehogs, neighbor's cats, and quite a bit of crawling critters when the window was open. When my husband wasn’t home, I didn’t dare to sleep with the window open – anyone could have just jumped over the fence and come in. So I actually had bad experiences

A bedroom facing northeast would be ideal, right? Kids’ room / office facing south, since the view there seems unobstructed? Apparently, on two sides there is only greenery – wonderful

A northeast bedroom is of course absolutely top, no question about it.
Hedgehogs..? sooooo cuuuute.
Of course, everyone has to figure out for themselves how that feels. For me, though, it was just perfect. The original poster can read plenty of suggestions here to find what suits him best.

My idea of "preparing for old age" would rather consist of the thought of getting rid of an inappropriate property again.

Exactly. On the other hand, the OP is considering installing a second kitchen in the basement of a house where other people will be living long before she retires. That’s possible, but not at the same time as saying "the general contractor didn’t understand our budget." Cure does not come before the duty is done.

Gladly. But how to proceed? Currently, we can only present offers from prefab house manufacturers. The 2 regional general contractors have quoted prices that are significantly above our budget. We are still waiting on others. We lack a bit of guidance on the proper procedure

Assume that the price of the regional providers is realistic. They know the area and the problems that can arise there. If you have no real idea what you want, make a list of requirements and lay it on the table for the contractor. Do not provide floor plans, only text.

Assume that the price of the local providers is realistic. They know the area and the problems that can arise there.

Above all, they have their reputation to lose. The big names can quickly hide behind franchisees "whom we unfortunately had to part with" or salespeople "on their own account" if caught being tricky. "The price doesn't taste sweet enough" is an indication that it is "more complete" than the "cheaper" offer; and if it is "too high," the house is too big or the faucets are too golden. Then you have to cut back (not paint – but I already said that). Asking around until you get the biggest possible house for the desired budget leads to all sorts of things other than happiness.

I have roughly put something together for now. On the upper floor, you could possibly turn the playroom into a dressing room. I quite like the basement as it is so far – however, there would only be one light well window in the bathroom. Maybe you have some ideas and suggestions for improvement.