This very common method is one in which the property owner acts as his own contractor. The owner-builder seeks out competent sub-contractors to the best of his ability, chooses the contractors he wishes to use, and coordinates the project and building schedule. Some savings are realized by the lack of overhead and profit margin that would otherwise go to a general contractor.
Other benefits include personal control over who does the work and at what price. Furthermore, the owner builder can jump in and do some of the labor personally thereby saving even more. An owner builder can expect about a 10% savings over hiring a general contractor.
On the negative side, there is no way to really know if the sub-contractors are going to do good work. Sometimes cheap labor can cost more than you had bargained for. A low bid from a contractor sometimes means they have less overhead than another. If less overhead means less liability and workers compensation insurance then your project could be delayed indefinitely and with much more cost.