Everything depends on your budget. If you can afford a better printer and you can dedicate time and effort into this, as well as put a decent amount of money into it at first, you can basically do just about anything. You should do some quick projections and see how much it would cost, and how long it would take before you are actually turning a profit (debt is not fun). Find the printer you want, add five or so tanks, vats, rolls, spools, whatever of filament/resin. (whatever fits the printer, obviously), as well as whatever costs you might have, such as shipping, renting a website, eBay fees, etc, and then estimate your monthly profit, and see how long it would take to even out. If you do the math, you may want to change your mind, so keep that in mind. Also, before you even buy the printer, get familiar and good with whatever 3D program you are using. You might need to take a month or even more to get good at the program before you start the business part of your idea.
If you really do want to start out and sell these things, I would recommend that you first master 3D printing, modeling, and whatever else you would need. I also recommend getting a website, in addition to possibly selling on 3D printing websites. This would help give you the most chances to be seen and for you to receive more business.
If you are going to be making 70mm figurines that are extremely detailed, your best bet would be an SLA or a DLP printer. They print with resin and lasers, making them extremely accurate and detailed. At the moment, (in my opinion) the Form Labs Form 2 SLA 3D printer is the best SLA printer, as it is big, detailed, has a great support team, etc. One thing that I think you should know, if you do use a resin based printer, (SLA or DLP), then you should keep in mind that resin is pretty expensive, and if you do get a high quality printer, most of them do not accept 3rd party resins.
For 3D printing programs, I like solidworks, but is is mostly for mechanical parts, and if you are going to be doing soldiers and livestock, it might not be best for you. I would recommend the Autodesk series of programs, as you can get them for free if you apply as a student, and you can try them out, see how you like them. I do not have much experience in what you want to do, so I might not be the best person to ask about what programs to use, but they can be a start.
The printer that I talked about, the Form 2, costs around 4000 dollars. It is pretty expensive. If you do not want to make such a big risk right away, there are many other high end SLA and FDM 3D printers that are more affordable, and you will have to do some research to find whichever one is best for you. If I were you, I would start off with a slightly cheaper printer (unless you can and want to buy the Form 2), and see how things go. If unfortunately things don’t work out, it is not such a big loss, as you only lost 2000 compared to 5000. If things go very well, and you get a lot of orders, you may want to invest in a second printer, but be sure to do the math and see how much you make, and see how long it would take for you to net a profit after paying off the printer.
Before you do anything that I, or anyone else, says, RESEARCH! I am not all knowing, and some things that I say to do or say may be completely wrong. Also, researching is good, as it helps you become acquainted and slightly more knowledgeable in what you are going to do, which is always good. Unfortunately, I cannot help you out with your profit margin question, as what you are proposing to make is a very specialized field, and I have no experience with small figurines.
I wish you the best of luck and hope that at least something that I said helps you.
