If you are a adult and actually can't afford internet there are many government programs that fully or partially pay for internet. Call one of the isp and ask them.
Otherwise it is not likely in your house. There are likely a number of public internet locations that offer free wifi like a library. Maybe some business also but most those really are only for their customers.
Not sure what you mean by "air card". There are many types of cards that use cell phone networks but I have never seen one that is free.
The problem is someone must pay for all the equipment and even simple things like electricity that allows any device you have to connect to their equipment. They have to recovery the costs to run this somehow so they charge people a monthly fee.
using my phone to have internet access, it is plugged to the pc by usb. I convert cellphone load to internet time, For example, paying 100 pesos is 6 gb all data valid for 1 week. I can access any site, download anything until the 6 gb cap is consumed,