If you flush everything and dip your entire boat in CRC/303 EVERY time it is exposed to salt water, salt mist, or a picture of salt, then you may not have any salt problems.
If you do NOT do the above then you will.
That said, there is a HUGE difference in a boat rigged for salt duty and a cheap freshwater boat. A cheap boat built for nonsalt usage will have a different grade of stainless hardware that will shine brightly in freshwater usage but will stain, corrode, or even rust in salt. A cheap freshwater boat will not have double grounding/bonding systems to ensure that ALL metal pieces on the boat are electrically bonded to eliminate galvanic problems. Vinyl quality, thruhull fittings, the thickness and grade of canvas/isinglas, placement of drains, and other details mark the difference in survivabililty of a boat in salt.
Even within the same brand of boats, different classes and sizes are biased towards different markets.
Sea Ray sport cruisers under 35' versus over 35' are a good example of different intended markets (hint: the bigger ones are better suited to salt duty).
Here is what a boat broker in FL told me (regarding cruisers that sit in the water):
New canvas every 2 years. New bottom paint every year or twice a year. Topside wax monthly. Metal polish quarterly. Bottom clean (with a diver) monthly. Spray down and CRC after every run or every windstorm (from wind driven spray).
Here in freshwater, my canvas is 7 yrs old and in like-new condition (I do moor in a covered slip). Wax twice a year. Bottom paint every 4 years. No need to spray after a run. Boats look wonderful.
I went to look at a Sunseeker that was 18 months old. I mean it was factory fresh 18 months prior. This boat had been run and put away wet every time. The gelcoat needed a deep buffing. The canvas looked ancient. Nothing else was hurt cause all the hardware and such was premium quality, but the degree of environmental damage amazed me...