#1 Avoid chasing the NIB concept. Owners reduce costs by $$$ buying distributor samples, private games, and other sources.
A lesson that needs to relearned for some, as it also helps moderate price increases.
#2 Restoring games
Private owners can afford entire collections with patience.
#3 Time - Most of the largest collectors have been collectors for years, which means planning purchases in advance, but always have money set aside that otherwise would have gone to other pursuits, ready to make a purchase when the time is right, constituting anywhere from $2000-8000 right now, if a person wants a "collector quality" late model game. For EMs and early SS $500-2000.
#4 Haul games and set them up for others. The effort adds up fast. It is extra income. You make new friends. You get better deals. You find more games.
#5 Know when to buy and not to buy. Understand the market. Do research. Buy in volume just like dealers and brokers. More games for less money. Refocus efforts on titles that are not "shiny". Do networking. Sometimes you can get still get games for free, if a person is not known as a "flipper". Collectors do each other favors for assistance.
This is not an optimal period to buy certain types of games right now, as currently we are undergoing, "The Age of Pintards".
Other methods are unrelated to pinball, but are to related to smart investments, and other supplementary forms that have been earned, not provided. I also raised children, so that was included over the past 30 years.