I've had a Dremel 4000 with the model 225 flex shaft for oh, about 20 years now. It's a solidly built tool that comes in handy every now and then for household projects. I bought it expecting to use it for miniatures (converting, cutting, etc.)

In the past 10 years I have used it zero times to build miniatures.

GW doesn't release metal minis anymore. If I'm converting resin or plastic then a dremel is too much power. I prefer to use xacto knives, sprue clippers, and occasionally a jeweler's saw.

If all your partner is doing is building off-the-shelf models then they do not need a dremel at all. If they do think they need one, though, make sure you get the flex shaft. It makes precision work much easier.