Well, I'd say A Titan of a Job if you are good at shooting and landing a plane. If you aren't so good at shooting it may take longer (it takes me a little time to do on my own but with a sniper rifle, a good car for cover that I can move (and also taunt NPCs into coming into view), I can easily clear the NPCs out and steal the plane. It seems the hardest part is landing the plane (which so far I've been able to do fine except when I frikkin forget the landing gear
). oh, and try to avoid missles into the hangar, if you blow up the cars in front of the plane you're going to have fun trying to get the plane out (and will damage it at least a little which will make it harder for you) or you might blow up the plane
. You really shouldn't need to do so anyways. I so far haven't had trouble clearing people out on my own and honestly, if I find it easy, so should you
(though I usually do so with some patience too. I don't mind taking my time and making things go to my advantage first. in fact I hate timed missions cause I flub up a lot more if I feel pressured to do so in a certain time).
If you have a buzzard, Trash Collection (or something with Trash in the name) is good. Also Denial of Service is pretty easy with a buzzard and can pay decently (or ok at least). There's also one where you gotta take out 6 people that's pretty easy in a buzzard (can't remember the name) that is really easy with a buzzard (both Denial of Service and that one are timed but with a buzzard you should be able to do it).
Also, steal cars. If you don't know where to find gang cars (I used to on the PS3 version but don't anymore on PS4), go for Ballers. They're worth 9k and you can find them everywhere. Hell, if you have a garage for space store them up when you find them and just sell them when you first log on or any other time you are bored and you haven't sold one in a while. No waiting for when they start spawning.
I just got 9k off a armored truck today. A sticky bomb and a call to lester and it took me a minute or two to make that (ok, so it probably was 8k if you consider the price for the sticky bomb and lester call. Hell, you can just outrun the cops too, I just never feel like it when I do that one, don't know why).
Take a heli and hit up a few stores to rob. It's not going to net you much, but it's easy money. Even 4 stars is pretty easy to outrun in a heli (you'll keep accumulating stars as you rob stores. Wear a mask, you'll accumulate them slower. You'll really only have trouble outrunning cops in a heli at 4 stars. Also, the frogger is best for this as it handles well and is decently fast for a heli. The one that has guns only sucks cause it's so slow. The buzzard gets damaged too easy. One slight hit into anything and you're gaurenteed it'll start crapping out on you in a few minutes. The other non weaponed heli that spawns is ok for this as well but the frogger really is the best one as it still handles better and is faster. The Frogger is honestly my favorite heli in the game. The buzzard is useful cause it has missiles and guns but the frogger is more fun to fly).
Basically, these are some of my easy ways and if I find them easy, they shouldn't be too big a problem.
Also, Rooftop Rumble is a favorite.