One of the things I worry about the most when getting ready for vacation - is keeping my cat, Marti, safe and happy when I'm away. If you have a pet - you know what I'm talking about.
Rest assured - leaving your loved one(s) safe is most certainly possible. All that is required from you - is a little effort. For example, Marti is getting up there in age. He's now 9. So I have to take a few more precautions. I would argue thats a good rule of thumb: the older your pet is the more you may have to do.
For me, the longer I'm gonna be gone the more challenging - and costly - it gets. If I'm going away for a weekend - one of those automatic food dispensers is perfect with some dry food in it. That way Marti will have plenty for two or three nights by himself. Before I leave I also make sure he has plenty of water and his litter box is clean. The great thing about cats is that you can do that with them. They will be perfectly fine for a few nights by themselves. Dogs - not so much.
Dogs need to be let out daily to be walked, go to the bathroom, and get a little exercise. So, if you have a dog, or a cat that needs to be watched while you're gone - you have two options: you can either call a pet sitter, or you can bribe a friend to watch fido.
2) It's not necessary (unless your circumstances are extreme).
3) It's not cheap. The pet sitter I use runs at $20 a visit. Admittedly, boarding your pet depends a lot on where you live - but most prices I could find range between $45 a day to over $200 a day.
The bottom line is this: you know your situation best. So modify - and do whats best for you.