Hello Adameee & welcome to The RV forum.
Folks on the forum are passionate RVers and we love to help other RVers. People new to RVing frequently have questions or need a little assistance in troubleshooting. We have a large pool of collective knowledge and can address most items. Much information has been collected and stored in our library. If not there, a search on previous discussions (threads) can be fruitful. And of course posting the question here works too.
To your question; You didn't indicate what part of the country you are in however the question it's self would indicate that you are in hard winter country. Keeping plumbing thawed can be both expensive and difficult. If the weather dips below 32 and stays there for a few days you could have major problems.
The answer is always heat. Many RVs have the plumbing running along side of the heat ducts. For this reason it is wise to heat the RV with the furnace. If you choose to heat by another means, then run the furnace fan to circulate the warm air near the pipes. If you rig has the plumbing running beneath the floor and exposed to the outside it is going to be a real problem.
Holding tanks are another issue, and need to be considered. But you can keep antifreeze in them.
The fresh water holding tank can also be a problem. However a trouble light placed in the compartment with the fresh water tank can generate a lot of heat and in most cases it will protect the fresh water tank.
If you get into sub zero temps, you are going to have problems. Some sort of barrier like skirting, hay bales, etc. will do a lot of good.
Plan on using tons of propane!
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Welcome aboard!