Deadbeat specifically means someone who doesn't pay back money borrowed, or debts owed, ever. A deadbeat borrows, and betrays trust of family and friends.
Welch is a person who defaults on an obligation, especially a small one.
A moocher or a sponge or a freeloader or a scrounger have similar meanings to each other, but different than deadbeat. All are cheapskates, consistently taking advantage of the generosity or obliviousness of others in a non - business context.
Note: These terms do not necessarily, or even customarily, refer to taking money, but rather, sharing a ride but not reciprocating as promised, sharing a hotel room at a convention but not contributing to the expenses etc.