That is quite impossible!! You need an offer to work from any employer that is if it is to work for someone else. You need an "oferta de Trabajo". If you have relatives or friends then that would be better since you can apply as an Au-pair or plain domestic or any other job initially.
You need an official "Oferta de trabajo". This is drawn up by your potential employer in Spain and is certified by the Ministry of Labor in Madrid. You will need the NEV (Numero de enlace de Visado). Once you have this you can take it to the Spanish consulate or Embassy.
You will need the following since you are applying for a Visa (Ajena)
1) Passport with 2 photocopies and 4 photos
2) The application form from the consulate.
3) Letter of good conduct from your city's police (police HQ).
4) The oferta and a copy
5) A medical certificate which is clear that you are not ill physically or mentally, not a drug user, do not have the plague, yellow fever, or cholera. Be very thorough with this.
After this you will be interviewed in the consulate or embassy then expect to wait for 3 or 4 months. Then you have your visa and can go to Spain.
Once you have the visa, when you arrive in Spain you must apply for a residency permit. This is done at the police in the area where you have your oferta or job, and will take a long time as well. You can also apply for the NIE. Your identification and will serve as another form of being "legal" in Spain. Once you have all of this you are legal so then you can look for a better paying job.
Hope I was able to help.
BAS
BAS