house buying - tax efficiency

[911newbie]

My partner's parents are getting on a bit and currently live in a large, draughty, three story barn conversion. So we're contemplating remortgaging our house (on which we currently have almost no mortgage) in order to buy a house outright for her parents.

Her parents can then sell their current house at their lesure and get the best price for it. (They're keen to avoid the stress of a chain.) Once they've sold their house they will buy the new house from us for whatever they get for their old house.

So my question is - what is the most efficient way to buy a house for the padres in law ?
We accept we may have to make up the difference between the value of thier current house and the cost of the new house, but we're keen to avoid unneccesary taxes/expenses.

Thanks in advance.
Chris

[911newbie]

Gentlemen, I can't thank you enough.
We had not thought about making this a loan, which is effectively what it is. This seems to be a much better idea. I'll get an accountant (or a solicitor ?) to set up the loan agreement.

Eric MC -
You are right about them never paying the loan back. Still we know where they live.. !!

We plan to remortgage our current house, which has only a few £k mortgage on it, to raise the money.
I would guess our mortgage company might ask us why we want to remortgage our house, and I hope the honest answer is sufficient for them.
I anticipate a delay of a year or so between buying the new house and selling the current one, so it won't be an instantaneous repayment.

[911newbie]

"Buying the house and selling it to them later will incur two lots of stamp duty."
- Yes plus two sets of 'valuation' fees and solicitors fees etc, all of which we're keen to avoid.
The idea of a zero interest loan seems to be very sensible.