There are so many variables that factor into any project that it is not fair for me to provide even a ballpark price. I’ve found that this often creates unrealistic expectations and false budgets. The best thing to do is schedule a free onsite visit so that a realistic budget can be established and all the factors that fit into a job can be viewed. A project of any size is worth taking a few small steps in the beginning to help ensure the best result possible.
There is little you can do when faced with limited information. Due to the lack of info, you will have to assume most of it. Such cases lead to conservative estimates and will most likely inflate the estimate beyond its competitive value. Rule of thumb estimates can be provided, but there is always a factor safety embedded with the cost estimates.
Other ways to tackle the problem is to enter into a unit-price contract. This way if the quantities or the scope changes on a given project you are secured from going over your budget. This also helps the owners to stay on the same page as far as the price, because the owner can verify the quantities with a relative ease.