I've found six inch diameter cutting wheels on an angle grinder to be fast, accurate, portable and effective. Great for sheet metal tool!
My chop saw hasn't been used in a few years, and my portaband only gets moderate use now. The angle grinder is much more VERSATILE, running wire brushes, rocks, flap discs, etc.
The thin discs cut far more easily than chop saw wheels, and aren't much affected by rough workpieces, rust, and so forth. I also use them on my Milwaukee portable circular saw.
An angle grinder (I use a 6" Metabo) and a Smith Toughcut torch setup plus some LP cutting tips would fit under 500 bucks new and be useful for MANY things for MANY years.
I'd start oxy-propane and hunt an oxygen cylinder on Craigslist and trade papers.
Once you have one oxy cylinder most LWS will let your "trade up" cheaper than buying new.