1. Deposit is always a must, unless you're willing to do it for free,
or practice the technique even it is not able to sale.

2. full stack is preferred,
as you may faces cases that required certain skillset.

3. Able to understand those messy codes,
or at least knew what it is doing,
able to rewrite to human readable and workable code.

P/S : You may need to upgrade yours or others legacy dinosaur tech code to new tech.