Hello, we have some experience of this and the short answer is that Trusts are expensive.
My OH was a minor when his parents divorced in the 80s. My FIL was very well-off at the time and wanted to secure a home for his ex-wife that her new partner could not benefit from.
So he bought a house (like you, mortgage free) in which she had a lifetime right of residence, but which was in Trust for their son (my OH) when she dies - she could not will it to her spouse. They are both Trustees and he is the sole beneficiary - her rights are to residence only. There was also some advice that it would lessen inheritance tax when passing to him.
MIL is still in good health, now messily divorced from her 2nd husband so glad of FIL's instincts in that regard! But the original property got too much for her to maintain and she wanted to downsize.
It took several months of referrals from solicitor friends before we could even find someone qualified to act for us in the transaction - it's a niche area. The original house sold for £600K or thereabouts, the new one was purchased for £450K, and the solicitors fees were in excess of £25K (from memory).
When the (hopefully distant!) day comes that MIL dies and we wrap finally wrap up the Trust, I have no doubt that it will be similarly costly and time-consuming.
So it's important to be clear on why you are doing this, and ensure there's no other option that would be more cost-effective. Best of luck!