Please take this in the spirit of our hobby - obsessive and compulsive. Wait. I meant "fun" :).
1. If you are new or old to the hobby, realize that the draw of pinball means something different to different people. From talking to other gamers (pinball, arcade, console and telecommunication devices), it may be to recover a sense of nostalgia - that nobody in the world will get except for YOU since it was about your life when you were younger and it triggers fond and wonderful memories of "when things were better and life was easier". It may be about triggering endorphins that just make you go bonkers and want to play "just one more game". It may be to help you get to meet people and come together over friendship and friendly competition. Whatever it is, don't be startled if other people don't quite get it. For most of the people here at Pinside they fall into one or several of the categories.
2. Remember to hug your family once in awhile and feed them - pets too. If you are blessed to have family members who are sharing your joy and love for pinball that rocks. If not and they are questioning why you are spending rent and diaper money on a new Teenage Ninja Turtles machine perhaps you may want to rethink your priorities. Always remember to take care of your family and self first, then charge up the credit cards for three limited edition Jersey Jack machines. I strongly suggest you also think twice about maxing out credit cards for machines.
3. Most of the people in the hobby are friendly, share information and are straight shooters. Please continue to keep the good energy going when talking and doing business with them. Bad apples float to the top and word gets out. Our community is not that large relatively speaking and being connected by the Internet makes it smaller.
4. A Top 100 list is meant to change. It happens in the music business, it happens in pinball. It is all subjective and it doesn't mean that if something is not on the list it is not a fun or addicting game. It just means people haven't discovered it yet.
5. Try to learn to do some basic repairs. It will save you money or time. If you don't have the time, then spend the money. If you don't have the money, be prepared to spend the time. Plenty of help here on Pinside and the Internet. Also remember that the original purpose of pinball machines is to be attractive, appealing and to get someone to put money in it to make money for an operator. They are commercial machines that are now household gaming machines. They are not always designed for maximum gaming play which is okay.
6. Expect that when you buy a pinball machine, you are buying it for the love of playing the game. If you are buying it as a collectible investment - that is a subjective choice. I use to sell as a side business comic books and collectibles. People would ask me "Is it going to be worth anything some day?" My answer would be "Does it make you happy? You should buy it if it brings you joy. It is just like a casino on the Las Vegas Strip, There is always another shining, lights flashing, noisy casino one block over to speculate with." There will always be another pinball machine coming out as a limited edition that you or others might want but markets are cyclical and change. Limited amounts of something indicates scarcity but not always desirability.
7. Generally speaking, if you have commited to buying one pinball machine, once you have one, you probably will want more. You will be limited to money, time and space. By adjusting the variables you can figure out if you have the room to get a second machine (space), the time to actually play a second machine if you are busy with your family (time) and can afford it (money). Make sure you clear it with your loved ones. It is not uncommon to have this story happen: "Honey, I just want to order one machine" "Okay, Boo. Just one." Two weeks later: "Why are there five huges boxes being dropped off in front of the house, Boo?" "They were just great deals, I had to get them. I love you so much."
8. Markets go in cycles so have patience. Machines that you want will come up for sale and then as you try to buy them, poof they are gone. Don't fret. Have patience. You may be pleasantly surprised that even something super rare comes up later on or something better.
9. If you have met your financial and family responsibilities and still want something - go for it. Pay the extra $200. If it calls out to you for nostalgia purposes, it won't break the bank or the price is right, take the plunge.
I am sure others will add on other comments but this is a reminder for me and hopefully some insight for others just coming into the hobby.
Stay safe and healthy everyone.