On the topic of how large of an investment a lathe can be for cue building you are one hundred percent right but two things you may not have thought of and actually go hand in hand.
Owning a lathe that is setup to do cue work, be it a dedicated machine like the Hightower Cue Smith series or the Mid America series of lathes, Or something like a Jet Gun / engine lathe allows you to work more efficiently, saves labor time and stress on your body and it opens the door to do other projects some of which will be related to cue work some of which wont be. For example, I had a small part break on my Harley the dealer did not have the part in stock and also they wanted an exorbitant amount of money for it. I was able to make the part in about an hour on my cue lathe using a piece of scrap aluminum I had lying around.
More importantly however, The lathe is not just limited to building a cue. You can use it to offset the cost or in my case completely pay for itself by doing repairs to friends, and fellow players cues. If your name gets out there as a person that does high quality repairs at fair or affordable prices you will end up with more repair work than you might know what to do with. The more repairs you do the better you will get, the more efficient you will get at doing them and those will transfer over to being a better cue builder.
When I service a pool table at a commercial location my cue lathe goes with me and I service the cues that are on location as well. I clean them, check the tips and ferrules, if either need replacing I do that, trim mushrooms, reshape tips. This serves a few purposes for me. It saves me from having to come back out and recloth the table in two weeks because someone tried to shoot with a cue that didnt have a tip and tore the cloth. It makes the owner of the establishment feel like they are getting more value for their money and also makes them feel that I am trying to protect their investment as much as they want to protect it themselves. At the start it gave me invaluable experience doing repairs and cleaning with out the risk of damaging my cues or an expensive customers cue. And most importantly it allows my name to get out to others as while I am there doing the table or cue work and other patrons come in they see that I have to the equipment and knowledge to do both and often I end up handing out 2 to 5 cards because either the patron themselves is interested in having some work done or they know someone who is. On more than one occasion I have gotten a call from someone saying "My buddy gave me your card, he saw you working at XXXXXXXX establishment and says you do good work, can you change a tip for me and clean my cue"
Just some food for thought