looking for a house at the moment as ours has sold, and theres 2 in the running, both in windermere

One house is asking 485k and is a semi with no garage. I reckon its overpriced, but we would be able to clear the mortgage on this over 20 years.

2nd house is asking 569k, much bigger, detached, same street as the first one, bigger garden with stream at bottom and double garage. With this one though i'm not sure if we would clear the mortgage.

I'm thinkng the 2nd house is ultimately much better and would be nicer to live in. We can afford the mortgage interest, and some repayment of it but probably wont clear it all. Now if this was the case i'm thinking we could look at selling in 18 years or so and down sizing as kids will have grown up by then as well. Then when we sell, clear the remaining mortgage and get a cheaper house to stay in forever after that.

Is this completely bonkers thinking? Anyone else in this position?

Theres also the fact the there will most likely be some family inheritance from my elderley parents before the 20 years is up, but i'm not factoring this into my calculations at the moment.

It seems like an ok idea at the moment as the LTV will only be about 45% max, so we should always be able afford something smaller in the future.