You have to gain points as a tax paying employee in order to benefit from this system and the payments that you receive are related to how much tax you have paid into the system. I believe that in order to receive full benefits, the minimum is 6 months on a forty hour contract or 12 months on a 20 hour contract but I am sure that somebody on here will correct me if this information is incorrect.
Business owners are unable to claim any benefits during the off season. The tax department determines how much you need to live on during the winter by looking at average rent, average shopping bills, average utility bills etc... across the island. In order to continue with your business the following year you must show that you have made enough post tax profit to live, based on the tax departments financial criteria. Bizarrely, they don't take into consideration how much it costs you to keep the business dormant off season.
If you cannot show the tax department that you have enough money to keep yourself through the winter then you must declare yourself bankrupt, then theoretically as a foreigner your residency is revoked and you must leave the country. Whether or not it is ever put into practise I don't know or how it affects Spanish citizens who are treated better than foreigners in this regard. Benefits in Spain although generous, are not the easy ride that they are in the UK.
Your best bet is to speak to your Spanish accountant rather than relying on this forum for information. This year the tax department and the ajuntamentos are very big on (one could even say fanatical about) handing out fines for any misdemeanours in order to fill their coffers. Consequently, professional advice is invaluable.