Quick answer
Get the field producing before you build the house. The saying is about sequence, and in that economy the sequence was survival.
Read both lines
Three lines and one instruction: income first, then the structure. The field was where the food and the money came from, and a house was the large, satisfying, visible expenditure. Reversing the order is how an ancient household starved in a nice building.
"Build your house" almost certainly carries its second sense as well, since this book uses house for a family throughout and 24:3 has just said a house is built by wisdom. So the counsel reaches past construction to a young man's whole sequence: establish the means before you take on the dependents. The saying does not scold anyone or predict disaster; it simply puts two good things in an order and lets the reader see why the order matters. It is the plainest verse in the chapter and among the most practical in the book.
Related: Proverbs 24:3–4 · Proverbs 27:23–27 · Proverbs 20:18 · Luke 14:28–30
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.