- Living by yourself in a separate fixed dwelling fully protected from the elements. A mobile home on a lot is fine; for this discussion, an RV/van/tent is not. Something like a granny flat or apartment above a garage is fine as long as it's all yours.
- Must not be subsidized or shared in any way. No living with parents, no government assistance, no roommates chipping in on rent, no housesitting/housework in exchange for reduced rent. All costs of occupying the dwelling must be covered by the tenant.
- Dwelling must have an area to cook and prepare food; a refrigerator; and at least one sink, toilet and bathing area, as a typical apartment in a developed country would.
- Must be a long-term lease or ownership; no discounts due to seasonality, property about to be torn down or seized, etc
- Include rent, water, sewer, trash, HOA fees, property taxes and other similar recurring costs necessary to live there. (Usually at least some of these expenses are bundled one way or 'tother.) Do NOT include variable costs that are possible to at least partly opt out of and maintain a "Western" standard of living. This would include electricity, TV, internet and parking. Also do NOT include routine maintenance costs that an able-bodied person can perform oneself such as lawn mowing and housekeeping.
- If it is a purchased/owned house, include either the mortgage payment OR, the monthly opportunity cost of the price of the house at 4%*. For example, for a house that costs $120k, this would be $120000 * .04 / 12 = $400. Easy way to do this is to just divide by 300. Assume no immediate maintenance is required, or bundle such cost into the cost of the house.
In the US the cheapest I can get this down to is the low to mid $300s, with electricity/heat another $40 or so on average. This is generally as cheap as it gets for 1br apartments in places with declining populations and aging housing stock. It is also around the imputed cost of smaller houses (~$50k purchase price) in the rural Midwest and Appalachians. Naturally such housing may come with other costs such as greater distance to groceries and the like, but I'd like to focus on just housing here. If you're willing to go into the $400s many more options open up in non-depressing parts of the country. I'd be curious to know the cost in other countries.
*This number was chosen because it approximates mortgage rates in many countries and as a side benefit is congruent with living off a 4% withdrawal rate. You are free to choose a different rate, including 0%, but I'd like have 4% as a baseline.