This section is the most difficult to describe, because every family has a unique situation. I determined, after creating an involved spreadsheet that spanned a year, that it was possible to attempt this without dipping into finances that were better left alone. This included consideration of financial obligations in the US regardless of where in the world we were.
Daily Costs
This depends on (1) comfort level, and (2) geographic location. Taking a taxi from the airport to the city center, rather than squeezing on to the metro, will result in a considerable cost difference. And taking that same taxi in London as opposed to Cairo also makes a difference. Accommodation preferences also vary widely in cost. The impact is minimal for a two week vacation, but months of day-by-day decisions on accommodation choice will end up determining how long the trip can last. Tours also add up. If you book a tour everywhere you go rather than hoof it yourself, it will be very convenient but expensive over time.
The most expensive places to go, speaking generally, are probably northern Europe (especially Scandinavia), the US and Canada, and Japan. After this would be southern Europe, Australia/New Zealand, South Korea, and portions of the Arabian peninsula. Further down is eastern Europe, and South America. The cheapest parts of the world include many destinations in Africa, India, and much of South East Asia. To give an idea of magnitude, one can probably travel for a week in India for the same price as one day in Iceland.
The way I budgeted the entire trip was to block out geographic areas and determine average daily costs. I tested this by looking at the average price for a hotel in a city, as well as for typical meals, some costs thrown in for museum or other tickets, and the transport to get to the next destination. For accommodation, which is usually the most significant daily cost, I generally aimed not at the cheapest, but near cheapest place that was not just a dorm room with bunk beds. What I found is that groups of countries fall into standard cost regimes and can more or less be averaged together. Sometimes only the largest cities stood out as being notably more expensive. On top of these daily estimations, I added the individual costs of taking flights or some special tour I anticipate that we will want. At the end, special lump sums such as travel insurance and household storage costs for the entire year were included.
So what does this look like in real money? Some examples (family of three, leaning toward the cheaper accommodation and transport options):
The UK: $300/day
Poland: $200/day
Sri Lanka: $100/day
Getting a rough idea of accommodation costs:
Getting a rough idea of transport costs, plus a great guide to travel routes and times:
Building a Cash Base
This is where early planning can really make a difference. Between myself and Janet, we were already working more than one job each, so working even more was not a realistic option. What did make an impact was budgeting the day-to-day costs in the two years leading up to the trip. We stopped eating out as much, did not go on many weekend trips, and did not buy new things for the house. The lockdowns in our area in 2020 helped, as it gave us an excuse to not do anything but be at home for weeks at a time. Additionally, I had some collectibles, and stocks, that I sold off over the course of a year. All of this helped, slowly, to free up money.