Hosting bills

I had some space left over on my vps so offered to host a few websites for my clients, they are only small monthly bills but I am getting sick of chasing them every month whats the best approach I they wont payment upfront for the year.
I am personally get sick and tired of chasing small bills

Well you technically have the power in this situation because they obviously want their website up and you could basically flip a switch and their website would go down.

Try and extend the payment time to like quarterly or set up a recurring payment that they can cancel straight away if they want. Should make it a lot easier to manage then.

Get a billing system like WHMCS and setup monthly recurring payments. If they fail to pay, late fees will be added and the account will be suspended after 5-7 days. Depending on your settings.