OK the PO of our boat did that. A good ladder is important. I did that on our first boat. I added a SS FoldAway ladder from Mystic Stainless (a bit expensive but they are the best.)
What won't work is to just screw the ladder top mounted to the toe rail. It needs to be through bolted all the way through with a proper backing plate inside the boat and of course bedded so it won't leak. The PO on our boat used 4 large SS wood screws on each side of the ladder into the teak
toe rail. It didn't really work properly so he did the same thing on the other side when the wood split / rotted and of course it failed there too. Failure to bed
a screw even the best Asian Teak
. They cruised the boat about 6 years so it got a lot of use. You really want the ladder mounted through the hull and I would use metal plates because they bed
easier and fit easier.
I would not mount it so that it protrudes from the side of the boat. There is just a good chance you will come into a dock
or a slip and catch it and do some damage. That was why I went with the Foldaway ladder since it can store up in the lifelines
folded in 3 sections with nothing sticking out and is self storing thus saving locker space. It was all 316 SS construction and you'll find 303 ladders look like crap after just a few years. 303 is strong enough just not salt
resistance enough. They are cheap
and what you find easily. They are just fine in freshwater.
Another way is to install to an outboard
T track so the ladder can be mounted to that and of course could be removed. Mounting T track requires backing plates
but are made to take large loads. I would use good metal backing plates
. AlMag is the best but others can be had too.