Typically, you need at least nine sets of building plans, as follows¹:

1. 1 or 2 sets for yourself
2. 2 sets for the general contractor
3. 2 sets for the plumbing contractor
4. 1 set for the electrical contractor
5. 1 set for the heating contractor
6. 2-4 sets for collecting bids (you should ask for these to be returned with the bids)
7. 1 set for the local building department
8. 1 set for the lender.