My advice would be don't bother. There isn't really any such thing as 'good' and 'cheap' the two words don't really go in the same sentence.
Using a cheap low end mig's isn't really an option, A lot advertise the machine capable of doing ally. The down side is they don't say to what degree you can successfully weld with them. Migging ally isn't the easiest thing in the world to do even with a good plant and it takes a lot of practice (A lot) to produce anything near half poor. Plus the cost of consumables isn't exactly cost effective to do the odd job here and there.
The realistic option is a Ac/dc Tig plant, again no such thing as cheap. Expect to pay £500 upwards for a second hand that's a near capable machine even for home use. Again the gas consumption and consumables doesn't really make it a realistic option for you just to do few brackets.
There are cheap end units out there but are normally nasty Chinese poo. So that choice is yours but expect to get what you pay for.
I'm sure others on here will add their views and machine options, you never know something might turn up that's suitable for you.
