Repipe house after tenant leaves, when I look for new tenant

[Kati Xi]

Hello all! My current tenant will leave end of April. I plan to repipe the house (due to unqualified piping material used in the 80’s) after they are gone. I reached a few plumbers for estimate and they all sounded very busy and I feel it is very possible the project will not be done on schedule. Shall I start looking for tenant now or shall I wait until the project is fully complete? If I start looking now, I am not sure what to tell the applicant on when exactly they can move in. But if I start after the project is complete then I am afraid that the house might be empty for longer than desired. I wonder what would be the best course of action. Thanks!