Tony houses are awesome but the biggest question is where can you park and live your tiny home once it's built?
Water. There are several options. Rain catchment and filter system (if legal in your area). A storage tank and have water trucked in. Well water. City water.
Water lines need to buried below the freeze line or run thru heated pipes/hoses.
Sewerage. Black waste would need to go into a septic system or into the city sewerage system. OR, go with a composting toilet and not have black waste.https://www.youtube.com/watch?v=_E2xOoNov9shttps://www.youtube.com/watch?v=dYR6GPmDzVMhttps://www.youtube.com/watch?v=5CdnVZkCKXU
Gray waste. "In theory" if you use biodegradable soaps, some say that it's fine to let it drain onto the land, even water the garden.
This too need be heater outside the home.
Electric. You can go with a 12 volt DC system, 120 volt AC system or a combination of the two. This can be run off city power, generator, wind or solar.
Heat. There are a lot of choices here from a wood stove, space heaters, heat pumps, in floor heat.
Interior plumbing. Remember that the heat needs to keep things from freezing. Having the plumbing on interior walls and to the living side of the insulation will help.
Also think about having a way to gravity drain the entire water system. Havinf pipes run down hill toward low point drains is a good idea.
Additional thoughts are welcome.