@Brian Garrett good luck on your project! I think it's great you are finding ways to make this happen. I would just be cautious about doing the work yourself, without pulling permits. You might get it look good, but if you have no permits it might not be safe or up to code and might make the house hard to sell down the road. There are certainly some stuff that does not require permits so those type of thing, might be ok but I would focus on the quality as well.
I think your question is hard, because the actual cost comes down to the details. Eg, how big is the home, what year it was build, what type of plumbing the home currently have?
For example, replacing a simple roof of 11000sqft home will be much different then complex roof on 2,800sqft home. The same goes for pluming. If the home was build in 1950, small leaks might mean all new plumbing. Or if the home was build in 1980's maybe the plumbing is polybutylene and again, will require whole house plumbing.
How big is the driveway and or does only small section needs to be replaced?
I know you might not be able to post the address worrying someone else might find or get the deal but without the details, it will be pretty hard.
Also keep in mind, most houses these days are already priced well with the cost of repairs in place and trying to get anything or even writing an offer under asking price is pretty laughable today. Not trying to discourage you but it's tough. The chances are that if the home is a good deal, someone already more experienced looked at it. If no one is bidding on it, then i would be cautious. Inspections are good start, but they don't check anything that the inspector cannot see so once you start opening walls, you might be in a big surprised. Some of the things you have described sounded like the structural integrity of the home could be compromised so it might be more then cosmetic things. Water damage can cause a very serious damage to structures.
Sorry I was not able to give you any specific numbers to help you but good luck, sometimes keeping it simple might be good to get started with. So if this does not work out for you, maybe finding something with a little less work and little less risk might be good to get your foot in..