plastic is everywhere so dont worry about that, its fertilizer
if you dont have good buy/sell prices then shipments of fertilizer is not going to work (i dont even bother with that at max buy/sell)
bags of fertlizer are better value and kind finf them all over the place
best way is with brahmin, brahmin add fertilizer to WB. theres a lady named kelly who wanders around the railway tracks by tenpines area that will sell you a brahmin for 100 caps 1/day
if you build brahmin feed troughs, you get a chance of one turning up too
but honestly forget all that, and do purified water instead
build say 2 or more industrial water purifiers at settlements and they will provide purified water into WB, my taffington with 3 of them puts 70-100 of them in each day.
you MUST empty them out each day to though, as they do not add to the water in there they overwrite it
you can have multiple settlements collecting the water and with max buy/sell they sell for 16 caps each
with my current character i do both jet and water but make waaaaaaaaaay more money from purified water because can make so so sooo much more
at a guess ive sold prob 10000 water and still have 4000+ awaiting sale in a container at level 54 character, i still make the jet for sale but buy everything with water
build water purifiers, i have 8 at the castle and 8 and sanctuary, i have a ferw more art spots like the drive in or taffington boat vbut really once you have 8 at the castle and 8 at sanctuary you are pretty much all set for caps and water, i rarely use stimpacks cause i always carry 15 or 20 bottles of water. with a charisma of 5 and 2 ranks of cap collecter prices are pretty good for the water.
Have you guys ever failed a settlement defense quests while you were activity at said settlement defending it?
i have about 6 or 7 turrets at sanctuary thats all, 15 or 16 settlers, defense rating is like 70 more or less, could be 60 something, i focus most of the defense around the house with the workshop and house across the street, i build a walkway from one roof to the other and have guard towers on it, and mainly the turrets are on both houses, 3 or 4 turrets on top of each of the two houses, thats my defense, sure it gets attacked but all my settlers are well armed with modified weapons like plasma, laser, assault and combat rifles they also all have combat armor so my settlers are robust, they aren't weak, with all the water i have,i buy good weapons and modify weapons i collect in battle, like quincy ruins they have a lot of combat rifles, i modify those, i buy assault rifles already modified and i buy plasma pistols and rifles and modify those, i also give some of the settlers modified laser rifles, and usually one settler at each settlement has a highly modified long range combat shotgun, so there's a mix of firepower and the enemies get mowed down for the most part pretty quickly, plus i'm there with a follower so most of the settlers don't even have to do anything, but my settlements don't get attacked a lot but they do get attacked.
well i've been there while the crops get destroyed, its a bit glitchy how that works, when i get the message to defend a settlment i get there pretty quick and stick around for the enemies to come and wait till it says "defended the settlement succesfully etc" then i leave, if you leave too soon it fails usually.
Sanctuary I walled off the 'rear' of it - I drew a line from workshop house to my house, walled it and then plugged the gaps towards the river which has purifiers - rating is 320 water / 138 defence, sanctuary does get attacked but rarely.
Warwick is W 123 and D 81 - that is atacked very regularly but its a fixed spawn point so very easy to defend.
Build shops as well - 1 or 2 Lvl 3 merchant yields 1000+ caps every few days but it needs a medium-large settler population in the same place so that they are buying stuff.
And then Jet - I actually combine with Flamer Fuel to make Jet Fuel which I find more profitable.
One thing - perks, magazines and other buffs e.g. charisma boosts can make a big difference. If you want to maximise profits its best to have a set of clothes that boost prices, also always sell to a weapons dealer as you just buy ammo to use as currency when they inevitably run out of caps