Depending on what county you live in, you may be required to do various testing before you can proceed with your projects.
Ours requires soil testing for pretty much every project. Septic, well, buildings, driveways, etc.
You have to get permits for EVERYTHING. We do have permits on file for 1 septic system and both wells have a permit through the state because wells are state level and not county. We will have to file for a new permit for the driveway, and all the crap that's in place because the previous owner again, did not.
Soil testing. This was all over the place. The first guy came out, drilled one hole and looked into it. Charged us $600 and that was it. I was told we couldn't build on the site we picked. I searched for another soil engineer. $600 to look at a drilled hole and no samples didn't help. I called and got a bid for $1800, that person comes and drills two holes and takes samples to send to a lab, except we had to pay the drilling team on top of his fees of $1800. Another larger firm in Colorado Springs quoted us $950 or so for two holes, two samples, and the report. Same as the $1800 guy, but there was no difference in what was provided. So when you need to get testing done, ask the county exactly what is required for the test to be accepted by the county and make sure that everyone provides the same services. We're basically out $600 because the guy didn't really do enough and when I asked questions about the report he gave me information which actually wasn't correct.
Same with plans. Know exactly what the county requires on your plans and make sure that every detail is on there and make sure that your house follows exactly those plans or they will reject you outright.
I thought I had everything squared away, but the reality is that I have no idea what the hell I'm doing and I had virtually nothing to work with, so months spent on paperwork and planning was wasted. It might even be worth the money to hire a person to do all of this crap for you because I'm just as confused as I was when we started, and am still flailing around trying to figure out what to do next. This time though, I have a ton of notes from the planning office and an idea of what we need, but I'm sure it's going to be one of those 6th time is the charm things.
I recommend if you are doing the project with a partner, have your partner also attend these sessions with planning department or include them on e mails with service people because they may understand information that you do not. We've been attempting to have me deal with the phone calls and administrative tasks, but then I don't understand something that he does and we lose money on the project as a result because my decision was based on knowledge that I didn't quite understand. So communication is key.
Research what is required of you. Understand the reasons behind the testing, plans, drawings, etc and make sure that everyone understands what it is exactly that you need from engineers, architects, inspectors, etc. Know that they will not remotely bend the rules. even if something is off by 1", you will have to redo everything. Be precise in your communication and execution of plans. I've wasted so much time, energy, and money by not making sure I understood the process.