Unless you are a licensed plumber, roofing contractor, or well drilling professional, you simply aren't qualified to evaluate these aspects of a home you want to purchase.
For this reason, when you have otherwise evaluated real estate properties and have decided to write an offer, make sure you make it contingent on each of the four professional inspections listed below. This way, if any problems are found, you can request that the current owner fix them or you can renegotiate the purchase price.
A Home Inspection
Having a home inspection is well worth the few hundreds of dollars it costs. These inspections are overall inspections of a property and are designed to point out major problems as well as smaller issues such as leaking faucets or dirty HVAC systems.
Home inspectors work for you as the buyer, evaluate the property without any emotion, and make the effort to find as many defects as possible. In doing so, they turn on the water, open all the windows, and produce a report you can use to get a better idea of how well the property has been maintained and what maintenance is needed.
A Roof Inspection
Though a home inspection is necessary to give you an overall evaluation of the home, home inspectors aren't roofing contractors, septic system experts, or well drilling professionals.
Though a home inspector will take a cursory look at the roof to make sure there aren't any glaring problems, you need a roofing contractor to thoroughly evaluate the roof for damage or incorrect installation.
A new roof can cost tens of thousands of dollars, and a leaking roof or an incorrectly installed roof will lead to expensive structural damage you will be stuck paying for years down the line.
A Septic System Inspection
Since the septic system is buried below the ground where you can't see it, it's important to have it pumped out, thoroughly cleaned, and then inspected by a licensed plumbing contractor. As part of the inspection, water should be run through the system to ensure the leach lines and drain field are performing as designed.
A Well Inspection
Lastly, but most importantly, if the property has a water well, then it needs to be tested and inspected by a local well-drilling contractor before you agree to purchase the property. The well needs to be tested for production as well as water quality.
In addition, you should speak with the drilling professional about the local geological conditions to determine if there are issues with hard water, acidic water, or contamination with arsenic or other naturally occurring elements that are harmful for people and pets.