It is advisable to get at least of three written budgets using identical plan and specifications so you can compare prices and contractors and do not automatically accept the lowest.
Make sure all budgets are based in the same set of specifications. Discuss the budgets in details with each contractor and make sure you understand the reasons for any valuations in price.
Sometimes a higher price may be worth it, if the materials to be used are of higher quality or the work is more extensive; e.g. if you are having your kitchen remodelled and one budget is based on installing prefabricated cabinets in standard sizes and another budget is based on installing custom made cabinets, the prize will not be comparable.
Beware on any budget substantially lower than the others. It probably indicates that the contractor has made a mistake or is not including all the work quoted by his competitors or the specifications had been changed. Special care in this situation.

Disclaimer: Daniel González Aranda through Survey Andalucía, assumes no responsibility for any damage that arises from any action that is based on these articles.
Questions regarding civil law, insurances policies should be addressed to a solicitor.
For a free consultation regarding technical questions or any other matter in relation with the published articles you can call at 686 846 624 or e-mail to surveyandalucia@gmail.com