I'm unclear OP if he's buying it outright for you or essentially giving you a deposit.
I am not quite sure why(!) but I can imagine feeling very stressed about this in your situation - like you're getting control back after things feeling outside your control last year and now they want to change your plans, somehow removing that sense of control you have gained. I'm not sure if that's the issue. It's just what I think I'd be feeling (and having people tell me I'm not being rational too, which is fair, because from the outside it's not rational).
Here's the thing though, just because you agree to go ahead, doesn't mean you'll find something immediately anyway. Looking will be stressful. The whole idea isn't your plan. However, as others have said, this ultimately isn't about the bricks and mortar as much as it's about giving you a security you can't actually imagine right now.
A friend of mine has a small flat. She left to go a live abroad and gave adventures. She left indefinitely but rented her flat out. Her mortgage was being paid and the property retained its value. When she decided it was time to come home (elderly parents), she gave the tenants notice and had somewhere to come back to.
I've another friend who never owned a place and she went away for a couple of years. When she returned it was a bit of a stress (understatement) finding a job in order to rent a place.
I can absolutely imagine this being panicky about this situation right now, and probably your DM isn't helping by pressuring you (which is probably just because she doesn't understand why you'd not be over the moon), however, take a bit of time out and mull it over.
What's the worst thing that could happen?
How could you avoid that?
Is there a way this could feel good for you - what exactly is the problem and can you get around that?
Do you need to write a kind of brainstorming list of the problems and look to see how/if they can be solved?
Just make sure if you go ahead that it's actually in your name solely and that in any future relationship you retain 100% ownership.