Does the facility have the space to accomodate this?
If your facility is one large room, plan for a general workshop with no electives. However, if you have access to several smaller rooms, you may wish to offer a few specific electives, giving your attendees an opportunity to attend one or two of them.
If space and tables are available, consider the possibility of inviting vendors to set up a display. This can draw more people to your workshop, and give you more outlets for your advertising. Renting table space is an enticing means of offsetting cost, but will likely deter many vendors since they don't usually make a lot of money at these workshops.
Costs vary. Several items may incur expenses.
If a packet of information is provided to each (pre-registered) attendee, the cost of these packets should be determined well beforehand. If the cost is to be offset, there should be a fee charged to those who receive the packet, or a cash sponsorship could be obtained through local businesses in exchange for advertising in the packet.
You may be charged a rental fee for the use of a facility. This can be offset by charging general admission to the workshop, or by charging vendors for display space. Keep in mind that the more expense you place on others, the less likely they will be to participate. Likewise, local businesses may be willing to give cash sponsorships to offset rental costs in exchange for advertising considerations.
Consider giving a gift to those who volunteer to be presenters at your workshop, especially if you are going to make a profit from the workshop. Without them, you couldn't have a workshop, so they deserve a share of the proceeds. If you are not planning on making a profit from the workshop, your presenters should be informed of this when they are asked to participate.