Will probably dig my own since contractors want retarded money. By the time I paid the digging for septics, site works, and utilities trenching I'd own 1/2 a light excavator or a cheap backhoe, never mind land clearing costs. But I digress.
The local council will have installation (and inspection) all clearly defined. Suppliers can give installation advice too but council will obviously have the final say. When my family sold the house I grew up in (on septics) we had to spend 10k to upgrade prior to sale due to changes in council regulations. Some places seem to be favoring composting septics over traditional, so if they're going to require it in the future you might do well to spend a bit more to install a more advanced system while the hole is dug. I've also read a few horror stories about new systems tho so I'm inclined toward the more proven age-old methods.
Idk if or to what degree you can compact earth over the tank and field. I remember a depressed portion in the yard at that house tho. If you've got doubts about settlement then maybe don't do killer landscaping too soon.
Obviously check on power, phone, water, and gas availability if you're looking at rural land. Power here is wildly expensive to extend. I'd be interested to hear what your research leads you to discover and which system you prefer since I'm gonna have to make my own decision as well.