I spent $1500 on my lathe, probably have $3000 in accessories and still buying them. A combo machine is a waste of money, the so called mill does not move, it just stays where it is which means you can use the cross slide with a vise to mill parts but you are very limited in movement because the headstock of the lathe gets in the way and you can't expect to mount something in the lathe and mill it with the mill because you can't reposition the mill to correspond with the part in the lathe. Basically, the mill just sits there and takes up space, gets in your way. If you buy the biggest lathe you can afford, it's going to be the best thing you ever did. Don't worry about tooling, because you can just buy one little thing at a time, even if the lathe has to sit there for several months because you have no money for tooling it's worth it. After you use the lathe a while, you may discover you never need a mill, because like I said, a lathe is also a mill, even though it's a little bit more limited than a mill due to the fact that the a mill has a large table, but to make pens, they are small enough that you can mill anything with your lathe. You need collets, a collet chuck or collet drawbar closer system. You can use collets to hold rods and make pens of course, and for drilling, but also, you can get a collet fixture that you can mount on your cross slide which would also have indexing and those can be found real cheap, so now you can use your collets not just to spin, but to adapt your lathe into a mill.
There's a billion types of collet fixtures, and this is just the first one that popped up in a search engine.
http://www.auto-met.com/subtool/stcat/st_pg7a.html
typically, they would have a larger base you can mount on your slide. You can just see the possibilities with one of these..I've seen ones as cheap as $30. That is how you use your collets to convert a lathe to a mill. Of course, if you have a regular vertical mill, you can also use a collet fixture to hold parts and do index cuts or holes.