In the original trilogy the Galactic Empire was built upon the Republic, so the newly created Imperial Military had all the Republic's immense resources and finances to completely reform army and navy, to be able to produce high-end machinery (like Star Destroyers or AT-ATs) and even to build two Death Stars.
But the First Order doesn't seem to have such a big industrial power behind it, yet somehow it manages to be able to train a considerable number of troops from an early age (which would require having large boarding schools and quite a lot of money and time to train the boys properly), to afford at least one Star Destroyer-class ship with a trained crew, a fleet of advanced TIE-fighters and even to be able to convert a whole planet into a Death Star III. All that is just impossible for a small "order", even if it may be founded on the remains of scattered Imperial Military. So the question is - are there any explanations as to where does the funding come from? Are there any major corporations or even whole sectors of the galaxy who sympathize the cause and are ready to finance the Order?