Vinyl floor on a roll is fairly cheap and effective. But I've found it to be a bitch to fit. Vinyl tiles are easier to fit. If the lodger habitually floods the floor, I'd be inclined to use the type that require separate adhesive rather than self-adhesive ones.
One thing I once did was sand down the floorboards, seal the cracks, and pour on a thick coat of polyester resin with a drop of liquid wax mixed in to prevent a sticky finish. That produced a very hard-wearing, impervious floor. It also looked good (better than any lino or vinyl IMO).
Frank