Yes sink carcasses are cheap, about £60-100 now.
However getting one out is not always easy - it depends on plumbing,
whether it is a corner unit etc.

Leaks can come from several areas.
Tap - do proper plumbing or use flex-pipes with shutoff ball-valves.
Avoid low height taps as their limited ability to get receptacles
underneath merely invites "bang flexion" against the pipes. Water
hammer can be (or become) a problem if you get new water mains - along
with pressure drifting up to extreme levels. Replacing w/m flex pipes
with new or better quality can help.

Overflow - in replacing some overflow chain the overflow "cup" must be
retightened correctly, otherwise it will weap continually with
splashes unseen often for years.

Drain - rare, but sloppy workmanship can create a damp area.

It is the unseen leakage that causes the damage, not the odd "spill".
Putting even a garden centre "large shallow tray" is sufficient to
catch it and spot it, small weeping leaks get missed until the bottom
of the carcass is mushy. The opening door does not present a problem
to "tanking", you just put a very low height baton across like some
carcasses already have (B&Q spring to mind). Practical "tanking" is
just a simple tray.