These variables include the location of the plumbing, the number of bathrooms, the number of fixtures, and the number of floors a house includes. Single-story homes generally cost less than two-story homes because the latter require more material to reach bathrooms and other upstairs plumbing fixtures. In many cases, the cost of professional plumbing will be much lower than repairing extensive water damage. Many homes built in the 1970s need to be repaired because of the outdated materials used to build plumbing systems back then (such as galvanized steel or iron).
Your home's plumbing system may require some improvement to fit the code, which also increases the cost. However, it's often best to replace the entire plumbing system at once, as old plumbing may be more prone to leaks and other problems that could increase your long-term costs. Every fixture or appliance in your home that requires plumbing contributes to the cost of installing a new plumbing. This is a great way to extend the life of hard-to-reach water pipes in your home to minimize repair cost.
Copper pipes also have a lifespan of around 50 years; however, PEX has a projected lifespan of more than 100 years, eliminating the need for additional piping (and the corresponding cost) within the owner's lifetime. It also reduces the amount of time and labor required to install the plumbing, which lowers the total cost of a household plumbing. When it comes to repair (or any plumbing work, for that matter), you get the quality of work you pay for. Whether you're repairing a section or the entirety of an old home, installing plumbing for a new home will be the biggest cost factor.
Another factor affecting the cost of replacing pipes in an old house is the size of the supply and drain lines. Blue-green spots often appear on sinks, showers, faucets, and other plumbing fixtures, caused by copper dissolving from pipes and integrating it into the water supply. The only reason I say that is because a plumber told me last year that it wasn't allowed by code and all the ads in the yellow pages say copper pipes are repeated. One of my properties was in an older district and after several leaks and complaints from tenants I ended up repairing a house with 3200 square meters.
I highly recommend people to research it if they are considering paying just my two cents and the way to pay it.