I take exception to your inaccurate statement that a sailor cannot make money buying & selling boats. I have made good money buying & selling every one of my boats, even taking into account the costs of necessary repairs & maintenance. As the last post stated its about buying low & selliing high. Many unknowing sailors simply pay too much for thier boats because they are green, & don't understand required maintenance. I bought my 1st boat an 1985 C 25 for $1,200. A put in about $1,500. to fix the keel trunk, recovered cushions, etc. & sold her for $7,500. That's a profit of nearly 5k. I then bought an S 2 28 ft. yacht for 5k, a good deal & did similar renovations & standard engine maintenance & sold her for $12,000. That's a profit of nearly 6k. I then bought our current C 30 for 9k, put in about 2k to bring her up to snuff, & will sell her for around 20 k when I'm ready. It's all about knowing what to look for: a good boat with a good keel, hull, working engine & sails, an attractive cabin, & regular maintenace performed. The boat can be a little dirty, & may need a haulout & bottom job, which helps to drive the price down up front.
As far as I'm concerned marine surveyors are a waste of money & are for suckers. I work as a professional building inspector, & I have never seen so many errors & ommissions as what the average surveyor gets away with. They typically do not run engines or generators, etc. if the boat is on the hard. They also do not typically go up the mast & thoroughly inspect the standing & running rigging. That means they have missed half of the major boat systems. Get a copy of the invaluable book "Inspecting the Aging Sailboat" by Don Casey, which contains a complete guide to yacht inspection, & a flashlight & rubber hammer to sound the decks & you'll likely do just as good a job as a typical surveyor.
Your $$ are better spent on a haulout & use your own eyes to see defects in the hull to keel joint, & running gear. etc. I do routinely hire a marine mechanic to perform a compression test of inboard engine cylinder health (or lack there of) & have a Pro. rigger go up the mast to give me an accurate assessment of the mast & rigging. This $200.00 of advice is still cheaper then an incomplete survey & is a lot more accurate.
You can indeed make maney on buying & selling sailboats, while upgrading,
if you are prudent, use common sense, & have an understanding of marine & mechanical systems; and that is no lie!
.... its not often people actually come out on top after selling the boat they have had a few years.