Lots of online guides for rat owning have a very privileged stance. Not everyone can afford or have the space to rat proof their entire home, buy a small army of rats so no one gets lonely, and buy a $200 cage. That’s all nice, but not necessary.

1. You don’t need to buy multiple rats if you’re sure your rat will have plenty of company. The only time that my rat can’t play with another creature is during the hours when I’m asleep. Aside from that, all day everyday  she has easy access to play with me or someone else in my family, and I often let her play with our dog and cats (under my supervision, of course.) However, they aren’t fish. You can’t just stick them in a cage with food and ignore them. They need lots of friends and attention, but those friends don’t have to be fellow rats. Owning multiple rats means buying a bigger, more expensive, cage, twice as much food, etc. Not everyone can afford it. 
2. Try to have atleast one rat proofed room. It doesn’t even have to be the room they’re in, or your bedroom. Mine is the bathroom. She can’t climb up anything slippery, so getting into the toilet isn’t possible. I keep the floor clean, and things up off it aside from a pile of dirty clothes that she likes to burrow in. Then she can run around the floor without any wires that can be chewed or places where she can get lost. 
3. If you don’t have a rat proofed room, just train your rat where they are and aren’t allowed to go. My rat runs around on the bed. She knows how to get down on the floor, but she’s pretty much trained not to. We’re still working on the training, though.
4. Give them lots of things to chew on. Chew toys made for small dogs, like small bones, are always good. Wooden blocks made just for small animals to chew on are also good. A bag full of wooden blocks (the one I got had like, ten blocks in it) lasts a long time, and costs around 5 dollars as I recall. The bone that she currently has to chew on was 98 cents. 
5. You don’t need to buy expensive rat treats. Rats aren’t picky. While you should buy store bought food mixes, atleast to start with, to ensure that they’re getting all the necessary nutrients, you can give them treats from around your house. My rat loves cheerios and rice crispies, popcorn, and any kind of vegetable or fruit. Just give them scraps of healthy things you’re eating for treats.
6. They will try to steal your food. Be aware of this and train them not to. Heather plays on my bed, and if I’m sitting on the bed eating she’ll climb up onto my shoulder and try to pluck the food off the fork before I can make it into my mouth. They will also try to climb up onto cups and have a sip.

If you have any other questions, feel free to leave a message. <3