Almost two years ago, I took part in running incursions on and off for about a month. This was to provide an income for my nullsec pvp. As one might expect, it can get pretty costly and if all you are doing is PVP, the coffers empty pretty quickly. It is rare that you will get a drop from a wreck that is worth selling. If you are solo, sure. You can goggle it up, get it to market and sell it. If you are in a group, it is pretty standard that the money from any loot goes towards the replacement program. Most corps and alliances offer a replacement program to their members in which salvaged wreck loot gets liquidated and pays for replacement ships. I wouldn't join a corp that does offer at least a momentary compensation. Some corps have a back stock of T1 frigates and cruisers and some of the larger corps and alliances have their own industrial wing keeping campaign from grinding to a halt. Of course, if you have a high sec need for ISK and you don't mind incursion monotony (as opposed to mining or missioning monotony), then you can pretty much print ISK by running incursions. They have had a serious impact on the market. Officer and more so, deadspace fit incursion ships fuel the market. It is extremely common to see 2-5bil incursion boats. Mauraders, as well as Faction & Pirate battleships rule the incursion lanes. If you don't have one of those ships or a T2 logistic ship, prepare yourself - you might keep getting passed over for incursion fleets. Unfortunately, you need to have the skills to properly fit an incursion boat as well as the modules or you wont even be looked at to join a fleet. Unless you are a successful businessman (trader, industrialist, mission-whore), its going to take some serious capital in order to get the nod to join a fleet.
On the plus side, once you have a dedicated incursion ship, you will make that ISK investment back pretty quickly. If you want to spend 10 hours running incursions, you will probably throw up a few billion in bounties. Yeah, they are that good. Of course, it depends on the fleet, how much DPS there is and how good the logi pilots are. If you get in a good group, you will make bank, bro. There are tons of fits out there, but the incursion fleets are broken down into two types: armor and shield fleets. The armor fleets are pretty good for newer players because they are more resilient. Shield fleets are good because they are fast, mobile and hard-hitting. When I was running incursions a few years ago, incursions were mindless. You just had to kill a set list of NPC's and move on. I think I recall that there was some changes last year (maybe not as far back) but when I ran incursions the other day, it still seemed the same to me. Perhaps the NPC's switch targets more and maybe that was the change. I didn't really follow it in the dev blogs and forum posts.
If you want quick ISK, you have the necessary skills and some starting capital (or a few PLEX) you can make a shit-ton of ISK for very little effort. There are many sites with incursion info and people post fits all the time. Anyway, Fly safe-ish.
PS, stay away from low sec incursions.. They are juicy hangouts for gankers. I got a Macharial kill when the pilot forgot where he was.