You probably want to save money by not using a general contractor, but using them as a resource is a great idea. What you are going to do is make sure you have all of your options covered. In case of the unforeseen, you might end up turning your project over to a general contractor anyway, so it doesn't hurt to find a few and get bids on your project right from the start. Their bid will be extremely helpful to you in planning and budgeting your work, but only if you can get the most thorough bids possible. So, when you ask for a bid for your project ask for the following:
1. A written cost break down or budget. This is something you will want to see broken down well so that you can see what each line item will cost you separately. It will help you see what your most expensive items are, and give you an idea of where you should look harder for a bargain.
2. Have them indicate in writing (with contact info) who will likely perform each line item. In other words, have them tell you which subs they are going to be using. This is especially important so you can compare this bid to that of the other general contractors you get bids from, and find subs that can do your jobs well and for great prices.
3. A written calendar of completion, or in other words a schedule that meets your deadline. You will likely want to have them draw up a schedule for a six-month project. Have them break your construction project down and show you how long each item will take.
When you ask for the bid remember that if they give you a good enough price, it might be worth using them, so simply be straight forward with them, and challenge them to give you the best price they can. If you tell them that you will defer building, go with another contractor, or build your house yourself if their prices aren't good enough, so you would like their best price, you will likely get it. Give them a chance to talk you out of owner building, and into using their services, but only if the price is right.

This approach will help you in two ways. One it will give you a more accurate idea of what your costs are going to be, you won't have nearly as much mark-up from the general contractor, and two it gives you an option in case you find you can't, or don't want to owner build after all.

Use the information the general contractors provide you to come up with your budget and schedule. They have been doing this for a long time, and likely will be accurate in their bids, with some mark-up. Utilize your resources well, and your budget and schedule will act as a money saver you did not even realize you had.