There are 2 ways to travel to Spain, either by getting a tourist visa at the embassy of Spain in your country or in the embassies of either of the 27 countries of  Schengen in your country. During the consideration of the application you can legally reside in the territory of Spain even if your visa expires, as Digital Nomad visa is an official residence for investors and grants the possibility to stay legally in  Spain for the purpose of application. FYI:  you will need to confirm your entry in Spain  by showing a stamp in your passport, your tickets or an entry declaration for the trip. 

Digital Nomad visa is granted for a maximum of 5 years depending on paperwork of each of the applicants and contract duration, which is a primary factor that defines the duration of the Visa from 1 to 5 years. 

If you are a remote worker, then you are supposed to work for 1 company in particular. 
If you are a self-employed professional and you can have service provision agreements with a few clients or countries, you have to show that only 20% of your income comes from the company based in Spain and the other 80% comes from other countries. Important.
You must be employed in the company for at least 3 months, the company should exist t least for a year, your total experience in the specified position should be at least 3 years or you should  have respective education, you CV should demonstrate your activities connected to the Digital Nomad Visa

If you are a self-employed entrepreneur, it is enough to register in Spain with the Social Security Service (SS), by paying the required taxtes to work for a foreign employer, whilst living in Spain. FYI: Spain has a double taxation agreement with 30 countries, which means that you are not going to be payng double taxes in both of the countries.

Yes, if you get your Digital Nomad Visa your family members can accompany you, as long as you prove significant financial resources to cover their needs. The visa holder – 200% of the minimum salary, so €1,100 x 200% = €2,200.
First dependent (i.e. your spouse or partner) – 75% of the minimum salary, so €1,100 x 75% = €825.
Further dependents (i.e. children) – 25% of the minimum salary each, so €1,100 x 25% = €275 each.

An employment contract when applying for a digital nomad visa to Spain is your main document. It should clearly state who you work for, how long, what is your salary and what kind of work you do. It is also important that the employer approves your relocation and confirms that you can perform all your duties remotely. FYI: All the documentation should be translated into Spanish.