I mean knowledge yes, money no (or at least not compared to a conventional army), and most knowledge can be obtained through the internet or people who support your cause (if you don’t have a reasonably popular cause you can’t create a grassroot paramilitary organization). Also remember that some of the bigger paramilitary organizations usually considered terrorists (I personally don’t like the term as I think it’s been corrupted beyond saving by Western politicians and media) control land the size of a small country, for example some of the ISIS branch organizations. Other than that some have state backers (see Qatar, Iran and the US) or gain money through people who support their cause or some kind of business activity (the Taliban sell cocaine for example). Hamas is a good example, and in their particular case the money mostly comes from taxes in the Gaza strip, Qatari and Iranian support and money sent by individuals from abroad (usually by Palestinians).

TL;DR: Paramilitary organizations usually don’t need as much money as conventional states, and have ways to get it. Add in a sympathetic cause and it’s doable.