There is basically no sailing situation in Saipan other than wind-surfing. You can anchor in the harbor. If there are any type of marina facilities they're very new and unknown to me. You may find a boat for sale in Guam but I wouldn't count on a wide selection or them being plentiful.
Guam, Rota, Tinian, and Saipan all have harbors with Guam being the only one of significant size. Once outside each of those harbors there is no other harbor or shelter to be found on any of the islands. You'll be sailing exclusively in open ocean outside the harbor and you'll find little room for sailing an ocean-going boat inside any of those harbors. It's one hundred miles approximately, if memory serves me right, from Guam to Saipan with no place to hide if the weather comes up. You'd definitely want a blue water capable boat for such voyaging.
Alternatively, you'd likely be very happy with some type of day sailer you can keep moored in Saipan and sail in the harbor and outside the harbor on the vast majority of days as well. Day trips down to Tinian, which is uninhabited, would be quite easily done. The wind is a reliable 15 knots day in and day out. The temperature an equally reliable 85 degrees as well. The cost of living is quite cheap and the beaches and the scuba diving are world class. A thoroughly miserable existence awaits you! (g)
Another reason a day sailer might be better is that, given the absence of marina facilities, you might find it easier to pull out of the water during typhoon season. While the Marianas do not get hit quite as often as say, the Phillipines, when they do it's a doozy! You'd have no way to pull a good sized boat from the water and anything left in the water is likely to be absolutely pulverized after a typhoon comes through. There is no real shelter and everywhere becomes a lee shore eventually during typhoon passage. Even in Guam all the ships put to sea to ride out a typhoon.
If you found a good boat in Hawaii, and I'd think that a trailer-sailer would be best, you could have it shipped to Guam, and then up to Saipan, in a 40' container. But you'd likely pay a premium in Hawaii so you might as well look in Ohio for one and ship it from there.
Living is cheap enough in Saipan that you should resist any urge to live on board a boat. While I'd not recommend sailing a small boat down to Guam or Rota from there, there are a couple of airline flights daily that are just a hop.
If you want to "go native" yet still deal with US dollars and be in a safe locale you cannot do much better than Saipan. Take one pair of flip-flops, a couple pair of shirts and shorts, and a swimsuit. You'll be all set for about five years or until the swimsuit wears out.
If you do not scuba dive don't worry about it. Look up Ben, or his son, on Saipan and you can take lessons from one of the best instructors around. And, instead of some swimming pool, your first dive will be in crystal clear water over a sunken Japanese Zero. At fifty four you might get the majority of good dives available on Guam and Saipan in before you leave this earthly realm.
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.