Many older homes in the Greater Houston area, those built before the mid 1980s, relied on galvanized steel pipe for water distribution. For the Houston area, galvanized pipe was considered a good quality material that provided a good service life. Typically, the service life of galvanized steel pipe in this are is 30 to 70 years. The life of this pipe depends upon factors such as pipe manufacture quality, thickness of galvanizing, water quality and water condition.
If your home has galvanized pipes, the brown water that is coming out of your faucets is most likely caused by rust on the inside of your pipes. And if you notice low water pressure from your faucets and shower heads, it's probable that you have calcium and corrosion scale build up inside the pipe which will restrict the flow. If you see leak spots on your walls or ceilings, the rust in your pipes has eaten its way through the pipe, creating pin-holes for water to escape. If you want to know for sure whether or not you have galvanized water pipes, you can go into your attic and look for grey or silver looking steel pipes. If you do have galvanized steel water pipes, look at the threaded connections because these areas are where rust / corrosion will typically start. Look for brown or reddish rust spots and for discolored attic insulation.
If you do find small leaks and faucets with low water pressure, just remember it's only going to get worse over time.
The only way to correct this problem is to replace the galvanized pipe with another pipe material that is currently accepted by applicable building codes such as copper, PVC, CPVC, or PEX piping.
As a Home Inspector in the Houston Texas area, this is one of the things I look for when inspecting homes. If you buy a home that has undetected water pipe problems, you will be the one paying to have them replaced. Better to have the seller replace these pipes before you actually close on the property.