There are several things that could cause that test failure.
For clarity, HUD generally doesn't actually test water pressure. Their inspectors usually check how long
it takes to fill a 1 quart container. That's a volume-flow test (gallons per minute.)
Many things, besides low pressure, can cause reduced volume-flow.
It's usually caused by rust or crud building up inside of piping within the home. Since "your" house is
from the sixties, it probably was plumbed with copper instead of troublesome iron. Immediate relief can be achieved by cleaning off the fixture strainer/aerators. It'll be back again soon.
It is my honest belief that you should not worry about it too much. Worst-case, ranch houses are easy
to completely repipe.
I do not know of any plumbing repair that can be achieved for $150. Maybe replacing a $.15 valve seat.
Go after the homes whole-heartedly. They all have flaws. Enjoy the adventure together!