Replace it before you move in. There's nothing worse than waking up to a giant rush of water running down to the street from a hole it's eaten in the ground. That's if you're lucky and the ground is sloped that way. If you're unlucky, the break is right next to your foundation and undermines it enough to then have structural issues and moisture issues inside the home to have to deal with as well.

And while you are at it, assess the rest of the home's plumbing besides the main. If the main is bad, the rest probably isn't far behind. It's better to get that 15-20K expenditure out of the way first. I hope you're getting a concession from the seller to address this.

$15-$20K is way too high for a typical urban/suburban subdivision home to main hookup. (Unless a creative municipality mandates that only they can do the work, plus an "administrative" fee.)

If you're in a pre -1930s home with a municipal sewer system you might also want to check (or expect) a break/clog in that line too.

Nothing beats when that happens on Christmas Eve and you have a sewer in your basement. (Been there.) :-((

My guesstimate was for redoing ALL of the plumbing in the home. As I said, if the main needs it, the rest probably does as well. Supplies and drains. And the sewer.

My guesstimate was for redoing ALL

Got it.

I'm curious what the supply pipe was made of--copper, steel and yes, even lead. Where I am, lead supply pipes were in use until the 1950s. Lead solder wasn't banned till the late '80s.

The house was built in the late 40's and the supply pipe is steel or lead (not sure).

Thank you for your feedback - I will get the replaced as soon as possible.

Lizzie-
Not only will the replacement prevent an emergency, it will insure that: 1) you don't have a slow leak that costs big money in your bill before you realize it, and 2) that you will have decent water pressure.

It is probably galavanized steel. A lot of the 1940/50 era houses have that and it's trouble if you leave it. The new water supply line can be made from PVC or HDPE plastic piping which will last for many years with no issues and much cheaper than copper to install. It's a fairly easy DIY job if you want to save some money but you'll need to do some digging. The part of the system where your supply line enters the house and starts branching off may also be partially steel and that can be a bear to tackle.

If it were me I'd have the current owners get it fixed by a certified plumber.

Also, get the sewer lateral/septic tank inspected and corrected before you buy the house.

Just a few terms to wok with.

main - the pipe that the water system uses to supply water to your area, normally 6 inch or 8 inch pvc or iron located on the right of way or under the street

service connection - the small piping that connects the water main to the customer's water meter, normally 3/4 to 1 inch copper or HDPE tubing

meter - the device that tells the water works how much water you used so they can bill you for it

backflow preventer - a check valve located between the house and meter that prevents water from leaving the house and re entering the water main during a main break or flushing

supply line - the piping that carries the water from the meter to the building, this belongs to the customer

Also, when you replace the parts of the lines that are restricted you can get some leaks in weakened parts of the plumbing system due to higher flow and pressure.