Supervise the building of your own home and save thousands of dollars?

Or personally direct the construction of your worst nightmare that gobbles up several times your original budget?

Either one can happen to a first-time homebuilder, according to a professional builder-turned author, James J. Hasenau in "Build Your Own Home: A Guide for Subcontracting the Easy Way."

In his slightly mistitled book he outlines what amateur builders should know -- whether acting as their own general contractor or employing a professional -- about home building, remodeling or improving and each of the many specialized operations requiring subcontracting. The evidence, however, builds a case for professional supervision.

Opening chapters deal with labor and materials, land acquisition, financing and scheduling. Other chapters follow on subcontracting procedures in customary order. A full understanding of all the intricacies involved in supervising home construction will discourage all but the most resolute do-it-yourselfers. But for those determined few, Hasenau's book can help guide the first-timer past some sticky wickets.

Among the points he makes:

Many amateurs use unnecessarily expensive materials when cheaper materials would be as effective.

Factory-built components (roof trusses and pre-hung doors) should be used whenever possible, saving labor and usually being superior to on-site construction.

Failure to obtain workman's compensation insurance can leave the amateur builder open to huge claims if a worker is injured.

The building permit should be obtained, whenever possible, before the lot is purchased or as a condition of purchase to avoid deed restrictions that could interfere with building plans.

Standard American-made plumbing fixtures are preferable at any cost to assure availability of replacement parts.

A 23-feet wide house would cost more than a 24-feet one because of waste and extra labor.

Changing the location of a window or exterior central air-conditioning condenser unit could violate the building code.

To accommodate factors such as inflation, theft and accidental destruction of materials, allow for 15 per cent more than the base estimate of costs.

The reader of this book who still plans to build a house should bear in mind that the most capable and reliable subcontractors often are fully booked with jobs for professional general contractors. So, except in the leanest of times, who does that leave the amateur?

Also, subcontractors give their regular employer a better deal than a one-time builder. At best, acting as one's own general contractor is a hair-thinning exercise for the first-timer. He or she deals with "subs" who can go bankrupt in the middle of a job (as a painter once did to me) or just disappear. Hasenau advises amateur contractors to hold back 10 per cent of the amount due until a contracted phase of work has received the building inspector's official approval.

All in all, it appears, most professional builders earn their profit. The book that helps prove it -- and helps you make sure you get your money's worth -- can be ordered for $6 (plus 50 cents for mailing) from 6215 Six Mile Road, Northville, Mich. 48167.

John Kuhnle works for the Federal National Mortgage Association. His experience in building has been limited to castles in the air.