Actually thinking further, if she's used to buying investment properties, you can smile at DH and point out his mum will be looking at properties differently to you - you'll be looking for a property that you both want to live in for years, that will suit you, but also you get a good 'feel' from. You need an emotional response, not just a purely financial consideration.
You may find there's half a dozen 3 bed houses that are within a few roads of each other in your price range, the decision to by house 2 rather than house 5 often comes down to which one you like the best. You MIL with her 'property devloper' head on might be looking at which will increase in value quicker or have a slightly higher rental value, but if you plan to live in the house for 10-15 years, those things are irrelvant to you.
Oddly, this reminds me of a thead I read years ago when that OP's DH had been convinced by a family member who was a jewelery expert to buy a plain but big dimond engagement ring, rather than the sort of vintage style the OP would prefer, because it would 'hold its value more'. The OP couldn't get through to either of them that holding it's value when you will never ever sell something doesn't matter. They were thinking purely as a ring as an investment, not something to be worn daily until death, then handed to DC who also probably won't sell it. Property developers do often struggle to stop viewing houses as investments, but as a home to live in forever/until your DCs have left home in a couple of decades time.
So don't take MIL with you. She'll not be helping you find a family home, and you don't need an investment.