As far as buying to make money seriously I hardly have enough money to buy a Seconda nowadays , I started buying when still young and started attending auctions in the mid 80's, in that time I cannot think of any area of collecting that has seen such growth in the last 15 years especially, I used to buy various incarnations of Speedmasters mostly 1960's 321 models they could be had in the late 80's early 90's for £100-300 in very good condition, 806 Navitimers could be had for the same money, I once bought a Rolex Military Sub at Fellows and Sons for £800 and sold it for £1,100 about a year later, I really could weep at that one, no dealers would touch them at the time because they had to change the hands, and drill out the solid spring bars and fit a Rolex bracelet just to sell them.
Money has entered the game in a big way now and prices are crazy and auction commissions are crazy, when I was buying you paid 10% at pretty much any auction house but some local auctions at that time where as low as 7.5% now the norm is 25% to 30% plus vat(tax) on the commission this has dwindled any returns that may be had.
I see so many frankens, marriage's or just downright dogs dinners fetching silly money now.
having said that it does make it more exciting now when you do come across a bargain or spot something that is way under priced
I think money can still be made if you work at it full time and know your onion's because fakes are every where.