Credit goes to Parasoja (not his ingame name, but its not hard to figure that out)
If you have an original blueprint (BPO) you can make blueprint copies (BPC) with a certain number of runs. BPC can be sold on contracts,and are bought by people who want to manufacture a ship without buying the BPO. Once they have a BPC they can manufacture a number of ships equal to the number of runs on the BPC.
capital blueprints are best for this if you are looking for passive income: They have a long copy time and a maximum of 1 run per copy. This is much simpler than battleships, which have a maximum of 10 runs per copy and presumably can be copied multiple times per month, which would mean more time doing math, more time setting up contracts and more pain in the ass. Some like to produce BPC "packages" including all BPC's required for you average player to produce 1 Dread/Carrier + all standard capital fittings/fighters. I left this out of this guide for the reason above.
There are a total of 22 possible capital blueprints:
2 industrial ships
There are several way's to decide which of these is the best to invest in, the best I've seen is Parasoja's: The value of the BPC in millions, divided by the number of months it takes to copy, divided by the price of the BPO in billions. The resulting number is the monthly return, in millions, for each billion invested. This number will be referred to as MMPB (monthly millions per billion).
Capital industrial blueprints are not sold by NPCs; I believe they come from players working for the ORE corporation. Consequently, the BPO cost can be highly variable. Although 3.3 billion seems typical for a rorqual BPO, putting its MMPB at around 32.
Mothership BPC before dominion ran about 1 billion across the board. After dominion this changed radically, with the wyvern and hel BPC remaining stable or decreasing but the aeon BPC doubling in price and the nyx BPC tripling. This is because the new supercarriers are damage dealers meant to be used in capital fights and the nyx gets a bonus to damage while the aeon has the highest hit points, making them very desirable. Since peaking around March, nyx and aeon BPC prices have stabilized somewhat, with nyx mostly decreasing to 2.4 and aeon down to 1.2-1.7. Wyvern and hel have dipped as low as 600-800 million.
Copy time is for science 5 with no implants
BPC prices updated 2011-2-9
You can easily see here that dreads are a suboptimal investment, however, if you have isk to burn it may be worth grabbing the dread BPOs and researching them early, as game mechanics have been know to change, you don't stand to lose anything except opportunity cost as the BPO should be considered equity.
There are a few factors which you may wish to take into account when picking which BPOs to research:
Utility. If you think you might have need of capital BPC at some point then maybe it would be better to get a variety of blueprints.
Market fluctuations. Investing everything in one type of blueprint will leave you vulnerable to price changes. If you get 10 chimera blueprints and their price drops significantly, you'll lose out. Spreading your investment over multiple type of BPO will give you lower profits but more stability.
Copying slots. You get a maximum of 11 per character, and although it's easy to train another research alt this will make things more complicated. If you have enough isk to fill your research slots it might be better to buy fewer but more expensive blueprints, perhaps going with freighters or rorquals instead of carriers.
Now, before we can start copying we need to research material and/or production efficiency. Looking at contracts we can see that the typical freighter blueprint copy has 3 levels of material efficiency (ME) and 0 of production efficiency, while carriers have 2 of material efficiency and 1 of production efficiency. If you like to play with spreadsheets you will find that higher ME levels than these do not significantly change the component requirements to build these ships, and manufacturers know this so there's no point researching them higher. As an example, an archon costs 516 million to build at ME0, 510 at ME1, 471 at ME2 and 464 at ME999.
For carriers and freighters each level of research takes 2 months, so once you have the blueprints you're looking at half a year before they start to produce. What's more, it actually takes longer than this because all NPC stations have ME and copy jobs in all their slots at all times; you will probably never see a research slot for those which doesn't have a wait time, except maybe in NPC 0.0. If you're okay with moving your BPO to lowsec the wait times there are much lower, or you can avoid wait times by using a personal research pos or renting slots from an organization such as New Eden Research, though both of these will introduce overhead and increase the amount of work you have to do. Do not, under any circumstances, keep BPO in a conquorable station.
There are also some implants you can use to speed the process a little, reducing research times by a maximum of 5%. At 120 million isk the 5% implants don't look like a great investment except for the copy time one. For me, a bonus of 5% would be worth 18 million per month, taking 7 months to pay off -- not bad for a long term project like this, provided you never lose the research clone.
The implants are as follows:
zainou 'beancounter' I40, I50, I60 - production time research speed bonus
zainou 'beancounter' J40, J50, J60 - material efficiency research speed bonus
zainou 'beancounter' K40, K50, K60 - copying speed bonus