If you're considering buying an old home, or one that has had a lot of "DIY" repairs and remodeling, expect to spend an additional $10,000 to $50,000 repairing and updating just the plumbing and wiring.
I see so many posts in this forum about people with questions about plumbing and electrical wiring with regards to their "new old" home. I suspect that many of these people jump in to old-house ownership without truly understanding the cost of repairs. Judging by their posts, many of these people assume that the repairs can't be that difficult, but the nature of their posts also suggests that they have neither the experience nor the expertise to do the work efficiently or safely.
My advice? Before you purchase the home, after the inspection, also have a reputable general contractor, plumber, and electrician (and any other necessary contractors) give you estimates on the cost of doing the desired and necessary repairs. Explain to them that you are seeking their advice as consultants, and offer to pay them for their time. That way you have no psychological obligation to use their services after the sale.
Even if you plan to do the work yourself, knowing the cost to have a professional do the work serves both to help you make wise decisions and serves as bargaining chips in negotiating the price of the home.
And if you do plan to do the work yourself, educate yourself. I recommend that you get books on the various subjects you need to learn so you get a more complete understanding. 0nline forums and YouTube videos are helpful, but not nowhere near comprehensive. You can learn a tremendous amount by yourself, but that still doesn't replace practical experience gained alongside a professional. It's true for any discipline: plumbing, wiring, building, cooking, driving, logging, brain surgery, rocket science, or underwater basket weaving.