Are you asking about taking the fiberglass top portion of the mast out of the lower aluminum portion or are you asking about taking the wires off? Separating the upper and lower mast is not practical/possible, but taking the wires off the mast is a twenty second job if that. Hang the mast under the eve of the house. It's out of the way, mostly out of sight, and protected from the sun and elements. I have a spare mast hung on the back fence, but on occasion my wife will ask me when it is going away... ...that is why the out of sight part is important.
By the way, the boat you are looking at has a couple of issues. The welded wing and new sail makes me curious. Wing tub damage is common, but how bad & where the tubes are damaged (mid tube split or base broken?) Where is the old sail? How did the wing arm break? The new dacron (not Mylar) main looks like light weight cloth. The new line makes me think the boat was redone for sale. Where are the old parts? If the new parts were bought with the sail, why is it being sold so soon? Find out how much a new Hobie sail and battens would cost. You may want it down the road. I bought my last boat used (sight unseen) and it had a couple of things I had to deal with, but it was inexpensive and none of the problems were deal breakers. You just have to know what you are getting into.
The 17 was designed as a single handed boat, the jib powers the boat up, but is still best sailed by either one or two lighter people. If this fits your plans, good luck. If you need more boat, the 20 or old 18 are bigger, but both are just a little more complicated and there is more stuff for the crew to sit on these two boats.
It does look like an inexpensive way to jump into the sport, so I don't want to squash your dream. I do want you to be able to ask the important questions. As long as the repairs are done well, it will be a fine boat for cruising.