Salt water can be done on a budget I set one up for my dad it's a 190 Litre tank.
It's runs a fluval 406 external filter and the standard internal filter that is it.
A powerhead to aid flow in the tank
He changes 25L of water every 2 weeks and has no issues at all so it can be done on a budget just stock according to filtration.
You will however struggle to keep any other corals ect softies as you will struggle with stability
Here is my dads
It's been running over a year so proves it can be done on a budget just have to be selective on stocking
The GSP at top is closed as light had been off and was turned on for picture