My units are melamine so I am going to paint them to freshen them up a bit. Is it possible to paint worktops as I am on a tight budget and can't afford to replace them.
You can paint worktops if you have to, but you must prepare the serfice properly or it will look like a pig. first you would have to rub the smoothness off the top with a fine sand paper or wet & dry to give the paint a good key, and also use good quality paint. Probable a roller would give the best finish. You don't want it to scratch easily or peel off.
Best to call in a proper paint shop for this advice, or ask a painter & decorater if you know one, they will know of all the different types of paints & primers which are suitable.
you would at least have to use a paint with a hard finish.
Any paint applied to the worktop is unlikely to stand up to normal wear and tear, and would be vulnerable to scrapes and knocks. Perhaps a final couple of coats of a high quality clear floor varnish (like Sadolin) would prolong its durability. It's used on shop floors, and puts up with people walking and scuffing their feet all over it. Only a suggestion.
Please don't!!! You will regret it if you do. You will , shortly end up with paint chips in your food. A high quality two part epoxy based paint is the only thing I would take a chance on. Good luck!!