If you wish for each home/lot to have their own septic tank, counties or city code will usually require a minimum lot size (1/2ac - 1 ac min roughly). Since you said tiny homes, this is probably not an option.
Septic fields are an option, but they can require a quite a bit of open space. Best advice is to reach out a septic designer and see how many drain fields you would need, or how many homes you can combine into 1 field based on code & practicality. In my experience on my commercial sites (with restaurants), roughly 1 acre out of the 4 acre site could be eaten up by a septic field. Not sure about residential though.
A well can definitely be set up to serve more than 1 home. Just need to see how much water a well in your area can produce, plus the cost / efficiency of a larger well vs multiple individuals.
In both scenarios with "shared" services, I would also give consideration to the shared responsibility & maintenance of the septic field , well, and equipment.