By no monetary gain, do you mean no collections at meetings and no charge for literature?
While it is true that they don't "pass the plate", as some churches do, they do remind their members of their obligation to support the organisation, and expect those who distribute the literature to contribute for it themselves. They also suggest asking for voluntary contributions from those who take their literature on the door to door work if they inquire about cost. If you go to the theocratic ministry school/service meetings on a midweek night, that is where they usually read out congregation accounts reports and reminders about contributions from members.
Also, a feature every assembly and convention I ever attended, and I attended a lot, is an announcement by an elder on the final afternoon, that the "cost of this assembly is £.....", and the "contributions are £....". The contributions are always well below the cost, and this announcement is followed by a plea to those present to make up the shortfall out of their own pockets. Many of the assemblies I attended were in halls owned by the watchtower society, where the only real expenses would have been amenities like water, gas and electricity, but even so the cost was always allegedly over £1,000 more than the level of contributions.
There is a financial cost to being a jw, and it's not the only cost. If you become one, you will be expected to give up your time and ultimately your freedom of thought to the organisation. However well-meaning these people seem to be, their leaders are out to control you. Stay well clear of them.