First are you a male or a female? If you're a male and 18 years old above your father can't sponsor you on a family visa. But if you're a female and single then you can be sponsored by your father on a family visa. Also you can be sponsored on a visit visa for 6 months. But your father should first get his residence visa before he could sponsor you on a visit visa. If you find an employer during your visit, you can change your visit visa to work visa. But as you said you don't intend to work only to take good care of your father. Then your father's new company can sponsor you on a work visit visa. It's better to declare your previous employment here in Qatar. If you are cleared, no obligations from your previous employer then no problem. Good luck,