I have a circuit in my house that has no power. This is a 20 year old house. Suddenly, there was no power to the outlets and lights in the master bedroom. An electrician came out and says that I have a break in my neutral/white wire somewhere between the breaker and the outlet. I understand that, but he also says that the main hot/black wire reads 3 ohms without power and needs to be replaced. I am having trouble understanding the black wire issue. Could the break in the white wire be causing the black wire issue. He is scheduled to come back and start opening walls.

3 ohms resistance is a lot in a short run. Standard is about 2 ohms in 1000 ft. Could be a partially broken wire or corroded wires in an outlet.

First determine which outlets and light work and which don't. Then turn of breaker to that circuit.

Again determine which outlets and light work and which ones don't. You should now know which outlets and lights are on that circuit and which one work and which ones don't.

Check wiring connections at each outlet and switch. If the "Quick Connect" holes in the back of the outlets were used to wire the outlets and switches, change the wires to the screws. The "Quick Connect" are notorious for developing bad connections after a period.

The bad connection can be at the last working outlet or at the first non-working outlet. Bad connection can be in the hot (black) or the neutral (white).

Highly unlikely that the wire in the walls will be defective unless you have done construction or repairs that damaged the wire.