In a perfect world woodwork and metalwork are done is separate rooms. Sawdust is bad for the nooks and crannies of precision tools, while cutting metal generates lots of oily filth liable to besmirch clean wood.
Of the two, sawdust is the most damaging. It removes lubrication from the delicate slide-ways of metal cutting machines by absorbing oil, and then causes rust because it also absorbs water from the air. It also traps particles of metal forming a kind of junior emery paper on moving surfaces.
Cure: keep everything clean all the time. It helps to cover machines with sheets. Clean working may not be your cup of tea! It seems model engineers split into two camps – those enjoy keeping their kit sparkly clean with everything tidily to hand, and me and my tribe who prefer to wallow in chaos.
My pillar drill is almost redundant since buying a milling machine. Occasionally handy when the mill is tied up on other work.
Once you own a metal lathe, it soon becomes apparent how desirable a milling machine is! Although lathes can be set up to do many milling operations, and the rest can done by hand with files, it's tedious compared with the convenience of a mill. Depends on the type of work done, but I probably spend more time milling than turning.
Due to a dislike of boring hard work, the most important tool in my workshop is the band-saw. Saves loads of time, cuts accurately and doesn't leave me in a bad tempered muck-sweat. When space is limited, it's necessary to choose tools carefully. (No point in having a lathe if the owner doesn't use it because he hates hacksawing.)
Lathe/Mill combination machines have an iffy reputation. Their advantage is space saving in small workshops. Unfortunately, like most combination tools, there's a price. The milling part of the combination lacks rigidity and the size of work it can cope with is limited. They don't compare well with a stand-alone milling machine with the same head. However a combination machine is better than not having a milling machine at all.
Unless money is very short, my advice is don't let choosing tools bog down in a mire of indecisive confusion. My main regret about getting into this marvellous hobby is the time I wasted dithering. Planning for retirement, with a range of other technical skills, I knew a lathe was useful and interesting but wasn't clear about exactly what I wanted to make. In the end, I got so annoyed with flapping about, I just ordered a mini-lathe and got on with it. The money spent on a mini-lathe was worth it for the education alone. Book learning is excellent up to a point, but it can't teach practical skills, or make the limitations of particular tools obvious. And practical experience makes it easier to understand what authors are trying to say.
A few years later, having mini-lathed various objects with much help from this forum, I knew exactly what I wanted and upgraded. Point is, you can change your mind later! It's not like the good old days when buying a lathe was a once in a lifetime commitment: today there's much more choice. In addition to a wide range of new hobby machinery there's plenty of affordable ex-industrial gear dumped on the market because the professionals have mostly switched from manual machines to CNC. Rich pickings when you know exactly what you want. In the meantime buy something, anything, and make a start.
Dave