I am not a plumber, but I am familiar with oxidation.  Many simple plumbing valves only need to be removed and new "O" rings installed.  That's where the problem comes in.  Most older homes used metal pipes and not PVC.  Usually the valve screws into a different type of metal and oxidation occurs between the two metals, almost becoming one.  In order to get the valve stem out you have to break it loose.  If you break the pipe, not only do you have a mess but then you have to pay to fix it.  Simple if you break it you pay.  If a plumber breaks it, he is responsible.  I recommend paying the plumbers fee and save yourselves headaches in the long run. 
Tree roots, corrosion, and debris can build up and threaten the healthy functioning of your home’s drains and sewer lines. When this happens, you need a professional rooter service to solve the problem and address your home’s plumbing needs. A rooter is a drain cleaning machine that was invented to unblock drains that have been clogged from tree roots and other hard to reach debris.
It does help in regards to procedures and rules in order to better understand your options.  Obviously cost is always an issue and the size of the company probably determine the labor cost.  That is why some times people take chances with "others' hoping that there have good experience but because they are independent operators there pricing might be more flexible.
I initially called Charlie's Rooter Service (CRS) due to a sewer line backup. Lulu answered and was very nice. She set up the appointment and Luis arrived on time and was also very friendly. He pulled out the largest root structure (out of my pipe) either of us had ever seen. We had a good laugh. He called it the catch of the day and had me take a picture of him with it.
Why don't I think it's completely hopeless though? (I'd probably rank it 3 stars being really generous) I think the writing is promising - it flowed well and was easy to read. The H's possessiveness and jealousy and alpha tendencies were nice and if not for him being a moron in every other respect I think I could've liked the book. Unfortunately the H being a moron and treating the h badly over the ow issue just killed it for me.
Get a minimum of three bids. Estimates for an average-sized job should be within a few hundred dollars. Be suspicious of anything that is substantially lower or double the price of the rest, and watch out for hidden fees, like charges for travel expenses. They could be signs of a home improvement scam. A good plumber will not nickel and dime you like this, and many of us will offer free estimates.
It is possible to prevent tree roots from obstructing sewer lines. Chemicals such as copper sulfate and potassium hydroxide can be used around the sewer line to discourage root intrusion.  Metal or wood barriers can also be installed around the sewer lines to keep them free of root damage. When landscaping, it's best to limit the amount of plants or trees placed in close proximity to sewer lines.
When you are faced with a plumbing emergency, time is of the essence. You don’t want to have to spend time searching for a plumber near you that is open nights, weekends, and holidays that won’t charge you exorbitant fees for immediate availability to address plumbing emergencies. Roto-Rooter plumbers offer a variety of emergency plumbing services around the clock at an affordable price, so you can get the plumbing services you need at a price that won’t break the budget.
Help! The toilet won’t stop running. It’s a bummer, sure, but it’s something you don’t need to call your plumber about. In fact, DIYers should take note that it’s a quick fix that will cost you just $5. For instance, your handle might just be sticking, which can be solved by spraying some lubricant where the handle meets the porcelain. Ready to DIY? Here’s how to fix a running toilet.

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