It can be hard to turn a descent profit unless you have a following at your location.

I had one location where I was making maybe 20-30 bucks a week between 2 machines after a 50/50 split. (not good, I pulled them after 9 months)

I make waaay more then that at my main location, it's just really competitive with operators at different locations. Like who is giving back the most on op gift cards, what prices you have your games set at etc... even after all that golden tee takes their cut and you also have to update your cabinets every year and it isn't cheap. Also computers will need to be updated eventually, it's not like pinball.

So yeah, I would check the Live wire map and see if there are other locations around first and see how they have their stuff set up. If you wind up doing it make sure you will be able to get the cabinet paid off in 2-3 years. Adjust your percentage to make that happen. If your friend is cool with that, then go for it.

Compared to pinball they are 10X easier to maintain. I clean the balls off with a drill buffer every week and clean the buttons out monthly, that's pretty much it. Might be a big issue here or there, but they are pretty easy overall.

in answer to your main questions, no it's not 20% it's .35 cents for most games. Other fees like updates, CC fees, Sprint fees (if you don't use LAN),
Yes use the live version, otherwise they won't be able to do the contest and stuff.

I wouldn't say that so much, just do your research. Followings can be built, it just takes a lot of time. Usually you will need at least two to gain that following. Even at that unless it's a high traffic location it still might not work.
It's not so much the fees or anything that suck, its the Operator gift cards that take the biggest chunk out of the earnings. last month alone I gave back close to 2k in gift cards. Gift cards are eared based on how many rounds someone plays.
I do
.25 = 30-50 rounds
.50 = 51- 75 rounds
1.00 = 76-100 rounds
1.50 = 101-200 rounds
2.00 = 200 and up
luckily I only have 3 people that hit the 200 and up, I make almost no money at that point. Plus on top of that all my games are $1 cheaper then the default pricing. Like I was saying it's really competitive here in Houston. Maybe you won't have to do any of that IDK.

Updates vary depending on your machine count, you get a discount if you have more machines. I only have 6 right now and pay 4300 a year
1-2 = 799
3-9 = 699
10-19 = 649
20-29 = 599
30-39 = 549
40 plus = 499

If you can fix a pin these aren't a problem, plus IT has pretty good tech support. Unlike other companies I've dealt with.
there is a reason you see these machines in every bar, but they might not work for everyone and every location.