Quoted from SantaEatsCheese:

I'm not too far away from you in Crofton Maryland and would give you a few pieces of advice. As far as distributors go, Pinball Star is drivable, and a good source for machines other than Stern. I say other than Stern because the quote I got from "Colorado Game Exchange" was about $300 less for a new machine delivered to my door than what I received from Pinball Star. My boss has picked up several NIB games from Pinball Star and has nothing but good things to say about them.
I too was worried about the technical difficulty of an older machine. In the 6 months I've had machines at my house, I've had a World Cup Soccer 94, Stern Star Trek, Attack From Mars Remake (current and for sale if you want to take a look) and Jurassic Park. 0 issues with the Attack from Mars (less than a year old), only a few minor things on the Star Trek (physically broken things that were obvious to fix), a few problems on the World Cup Soccer (overtightened nuts causing the motors to not spin properly and improperly seated wires causing lights to go out), and a broken board on the Jurassic Park (took about 6 hours to figure out and fix... I hacked the board). I honestly feel like diagnosing issues that comes up on these machines can be a fun puzzle. I wouldn't be too afraid of an older (90s) machine. If you are concerned with being able to maintain an older machine, get a cheaper one, keep it for a few months, fix it up (or don't) and sell it. If you spend 2700 on a World Cup Soccer, bring it home, but 300 into it fixing it up with new lights, rubbers, and a few parts to get it 100%, and then sell it for 2700 a few months later... how much did it really cost? It is a learning experience, and you can learn more about what you do and do not like in a machine.
I seem to be switching from a couple of A list machines to a mixture of B list machines. At the start of the year I had a Stern Star Trek and an Attack From Mars. I am in the process of converting that to a Jurassic Park (complete), lightly used Stern with Video (Guardians, Star Wars, or Iron Maiden), a favored 80s machine (Pinbot or Black Knight 2000), and a Mame Cabinet. That's pretty much an even money trade. You can set a budget and divide it up however you want. As long as you are not going NIB, you should be able to get about what you buy a machine for out of it (- most mods).
The best advice I can give you is to check out the awesome local scene there is in pinball near DC. The 3 places I go to (that are closes to me) are Crabtowne (30 ish mostly 80s-90s machines with a few new Sterns), MOMS organic Market (50 machines mostly newer), and VUK (15 machines mostly very high end). Between these sites there are 4 of the top 5, 8 of the top 10, 14 of the top 20, 26 of the top 50 on the Pinside 100 I can think of right now... all within 45 minutes of Baltimore. Most of these places have pinball leagues as well (I've never done them but they are there). Go play a lot of pinball machines and make a list of your top 5 or 10 and then wait for a really good deal to pop up local. Check Facebook Marketplace, Pinside, and Craigslist.
The other thing I'd highly recommend doing when exploring these locations is play the same vintage machine in different locations. By that, I mean play the World Cup Soccer at Crabtown, then play the World Cup Soccer at MOMs. This will show you EXACTLY how much difference condition can make in the playability and fun factor in a machine. Another great example would be the Adam's at Crabtown and the Adam's at VUK. As a side note do your self a favor and eat at Crabtowne. You can also play the "would I rather" game at Crabtown and decide something along the lines of, "would I rather have this Deadpool NIB for 5600, or this Fish Tales and Word Cup Soccer, or this Pinbot and Black Knight 2000 and Getaway. It's a fun hobby. If you would like an in depth tour of the underside of a Jurassic Park and/or Attack From Mars Remake let me know, I'm local.
Good luck and with very few exceptions (cough cough Shrek), all pinball is fun.
All in all, you are in a great place, for pinball.