I suggest you visit several greenhouse farms doing tomatoes and capsicums. Have an objective list of what to assess/evaluate. And don't be in a rush, revisit them after some months and see how they are doing especially those that are start-ups.
Tomatoes are all about timing the right season which is tough because everyone seems to end up timing the same seasons. The prices swing unbelievably. The positive side is that with greenhouse tomatoes you sell steadily through several seasons and get chances to recover from bad prices.
Gathige's advice up there #2 is very real and valuable.