I hope the OP reads the post above,about using a slitting saw on the lathe. Those type things were described in using a Unimat lathe,though I have never used one of them.I have seen the accessory list,though.
I would,however,thoroughly recommend that the operator keep his fingers out of the way of kick back. Remember that with some heat,metal might close up on the cut and throw the work backwards. Even a small lathe can cause a lot of injury to your fingers.. Always keep that in mind.
Since the small plane I posted above was made mostly with hand tools,I suggest that a few minutes with a hack saw and a file could produce the base plate of the telegraph key. The REAL work is the final smoothing up and polishing. Of course,with a lathe the size I recommended,you could mill it out.
I was pressed for money too,when I started out. What I did was save the money I made making tools for others,mostly collectors. I put that money back into the shop,buying better equipment. Everything I now have paid for itself. I have a policy of not using household income for buying my shop stuff.
You need to get connected to the Early American Industries Assiciation group. The EAIA. Pay the dues and go to their meetings. They always have the most delightful "flea market" of tools. You can exhibit your keys there,and almost certainly get a collection of followers who want to order your keys. You do need to remember that you will be dealing with experts,and get the details of your keys correct. Use your lathe to make those small parts like the knobs correct,and correctly knurled. Find correct slot head screws. Those things will make or break the money value of your wares.
I suggest that you buy a small horizontal/vertical metal cutting bandsaw ASAP. They are less than $300.00,and are invaluable time savers for the grunt work of sawing things out. I NEVER RECOMMEND HF. HF stuff is sometimes o.k.,but I think most of it is the cheapest pick of the Chinese machinery. You don't want to have your motor blow out. They often are cheap at best. I had a 3 H.P. TAIWAN made one arc across the bearings and had to be replaced. They do not dip their windings in insulating varnish. And,Taiwan is a LOT better than Chinese. Also,open the little gearbox if you buy one. Make sure there are no stray chips left in there,and it is lubricated,too.
Some here LIKE HF stuff. I am cautious about their offerings. with good reason. I buy twine and acid brushes there!
I distrust the electronics of Chinese things the most. I bought a JET wet wheel grinder,and it stopped working after an hour. I found out that the electrical press on connectors are literally as thin as beer cans. They crack when the operators push them on. I soldered mine and they work. But,that sort of thing is so crappy and irritating!! I was lucky to figure it out. All I got from Jet was garbage about how PROUD they are of their machines. DEALERS told me that those Jet grinders often do not work right out of the box. Mine was brand new too.