Different footwear dilemmas

I am starting my first semester of clinical in the fall and I need a good pair of shoes.
One of my problems is that I beat on my shoes pretty bad. I get a new pair of tennis shoes and within a month to 2 they are worthless, and I mean completely FALLING APART worthless. I'm a little heavier, so I wondered if that was the problem, but from talking to other people that are overweight who don't seem to have a problem with their shoes falling apart, I'm beginning to think its the way I walk or something. Also, after being on my feet for just a short time, they ache and so do my knees. (I think this has a lot to do with the weight which I am working on) I'm just so afraid that I'm not going to be able to make it through my clinicals on my feet all day. I'm also worried that I'll invest good money in shoes and they'll fall apart quickly.
Oh, I also have wide feet, so sometimes I struggle to find shoes in my size.

Any suggestions for a pair of shoes that might work for me would be greatly appreciated!