I started out with quoting about 15 posts, but I decided against it. I went out on my own 17 years ago as a G.C. Some things in this thread just crack me up.
1. I don't advertise and haven't for probably the last 15 yrs. I don't need the 20 calls a day with someone looking for the cheapest price. I know that isn't going to be me nor is it the work I want. I would say over 90% of my business is referral.
2. If you think G.C.'s are making 20% profit, I would like to get a hold of a few of them so they can teach me what I'm doing wrong. Don't get me wrong, I will add 15% to a job, but that is no where near take home. My insurance is around the $20k per year mark just for General Liability insurance, Insurance that I have to carry to cover projects under construction, tools and equipment. We won't even get into Workman's Comp, Unemployment, and having to pay 7.65% of wages for employee's or myself that the normal people that aren't self-employed don't have to pay. If I end up with 10% after it is all said and done, it was a good profit job. I still get to pay Uncle Sam on that 10% as well.
3. Most companies don't want to work with the do it yourself crowd. It tends to be more of a pain in the a** then the profit is worth, then you also have to question, I'm I going to get paid and how much screwing around am I going to have to do to get paid. A sub (I was one before I went out on my own) wants to work for a general because their screw around factor just got cut by 75%. They know they will be paid (A G.C. that doesn't pay his bills will set across the county in about 2 days and everyone will know in short order. Construction workers are like high school cheerleaders, everyone knows all the gossip. My subs never wait more than about 10 days for payment)
4. As a couple of the other people posted, I will find out what your rough budget is the first time I meet with you. If you want a Lexus on a Yugo budget, I'm not wasting my time or my sub's time bidding your job. I will however say that this project will require $*** budget and when you come to that conclusion I will be more than happy to work with you.
Now for the O.P.
It sounds like you want to be your own G.C. which there is nothing wrong with that. If you think you are going to end up saving 20% by doing it yourself, it won't happen. You will need to line up an excavator, a concrete company, a supplier for your raw materials, a framer, a roofer, a sider, an electrician, an insulator, a drywaller, a garage door company, a gutter company, a painter, a landscaper. You won't get the same price on any of this as someone that builds 10+ projects a year. You are a one time client to these subs and they will price accordingly. When it is all said and done, you will probably save some money, 5-7%, but you need to ask yourself if that little bit of money is worth you having to warranty the building yourself, and the amount of time you have to put into it, if it is worth your time. It might have some person reward that you did it. It might be a project that you can enjoy doing, but be realistic of what it is really going to cost to do.
I know I do a lot of things myself that aren't part of my job, like restore old cars, I save some money by doing it, but it is more about the finished product and saying that I did that. Trust me I haven't saved a lot, but I do have a lot of shinny tools.