"Do I have enough money?"
The first thing you need to know is that the total cost of your project is made up of both "hard cost" and "soft cost". "Hard cost" is also known as "construction cost". This includes materials, labor, and contractor’s profit & overhead. When you read about "cost per square foot" in magazine articles or ask a contractor what a project cost, this is typically the number quoted.
"What should I use for estimating my project's construction cost?"
To get you started (only a first guess), here are a few resources:
Free Residential Building Cost Calculator A free online calculator for new home construction from Building-Cost.net, that uses information from the National Building Cost Manual (published by the Craftsman Book Company).
Remodeling Cost vs. Value Report A regional report by Remodeling magazine of midscale and upscale projects for common types of residential remodeling project. Also lists estimated cost immediately recouped by the resale value of the improvement.
"How Much Will It Cost?" Published a few years ago by Fine Homebuilding, this is a helpful budgeting tool in a grid matrix format. Requires a paid membership to download (it's worth it).
"How Much Will My Kitchen Cost?" Same as above, but specifically regarding kitchen remodels. If you pay the membership, you get access to both articles (among others).
Don't forget the "soft cost"...
Expenses not included in the construction cost that the homeowner is responsible for are considered the "soft cost" of the project, such as surveyor’s fees, architect’s fees, structural engineer’s fees, reimbursable expenses, permit fees, and a contingency fund (see below). A good rule of thumb is to budget at least 35% for "soft cost". In other words, construction cost (including sales tax) + 35% of construction cost = project budget.
Have a contingency fund.
The most difficult costs to predict (especially when remodeling) are those which will be paid from your own contingency fund. You MUST have a contingency fund of at least 10%, and I strongly recommend 15-20%. The smaller the project, the larger the percentage. You will rely upon this fund to pay for unforeseen work (conditions that are not visible or predictable prior to demolition). You will also be presented with items during construction that usually include the phrase "...while we're here, it would be less expensive to go ahead and..." Part of my job is to help you differentiate between the "must do" and "would be nice to" items, and to think ahead to other items that may be triggered by these decisions (also known as anticipating the "domino effect").
And, sometimes you need even more...
Some projects have unique features which may require specialized services not included in "hard cost" or "soft cost", such as geotechnical engineering, soils testing, and environmental impact analysis. Landscaping, furnishings, and curtains, are not included in either category, so you will need to create separate budgets for those items.
How to Work With an Architect, by Gerald Morosco, AIA
An excellent step-by-step guide to the architect's role throughout the design and construction process.
Not So Big Solutions for Your Home, by Sarah Susanka, AIA
Regardless of what you discover about your budget, Sarah Susanka's advice in this book, and others in the series, will help you discover how to live large in less space.