Among the long term family cruisers/circumnavigators we know, there are lots of different answers.
Like BJ said all of the above. You find a way that works for you. Cruising around the world will not ever make economic sense. You either get over that, or you get over sailing around the world until you retire at least. There is always going to be some sacrifice.
I know several people who were successful small business owners, who have sold the business and are doing it off the back of that and I know some that do a bit of work as they go, and I know others who are on limited budgets for a limited amount of time. They are the common three stories.
What I can tell you is what our rough plan is. Subject to change, YMMV.
Our Boat: 35ft. 20 years old. Worth 100k. Payed off while still working. Major refits/upgrades undertaken now before we go, so no 'big ticket' maintenance while cruising( We hope).
3 years cruising with an option to extend on 35k a year.
We expect to spend far less in Asia and more in the Med if we get there. ( We are not necessarily circumnavigating, because of the Gulf of Aden/Cape Horn pickle- subject for another thread
Our total 105k.
We will rent out our house, which will cover the mortgage and give us something to come back to and help a bit but not much with money while cruising.
The balance of the 105k needed is just savings from blood, sweat and tears, not buying stuff, new cars, not going on holidays etc. Our get out of jail card is that once the 100k is gone, we can sell the boat and recoup the 100k back.
Our plan I guess can be summed up as 'cheap boat, low to moderate cruising budget, but with minimal financial risk'.
When the money is gone we sell the boat and come back. The house is untouched. We are free to cruise, but we also haven't sold the farm to do it. The perfect 'Have your cake and eat it too" approach? Will it work?? I don't know, ask me in 2018.
We could of however sold the house, bought a Hallberg Rassy and gone for broke. Trust me everytime I see one those darn pretty boats I am real tempted. For us though it wasn't the right fit. Other families are in different situations and have made different decisions.
For example if you can be smart about the boat you buy, how you buy it and what your plan then selling a house to buy the boat might be an option if your plan is a fixed 4 years. For this to work think buying a popular easy to sell 2 year old production boat, keeping it in good condition, and having in your plan that you will sell it in 4 years, hopefully only at a modest loss.
Several Australians I know actually have over the past few years bought a 2-3 year old Beneteau 40 something in Europe and sailed it back to Oz and sold it for a profit.
If you haven't already I would suggest having a good look at S/V Totem - a family sailing the world
. Behan talks honestly about what there costs have been so far and how the money is working out.