Well, you're going to be $250k into it, give or take, right? Are you building the house yourself and spending $100k on materials/permits/etc, or are you hiring out the job to a GC?
So using the 50% rule, you'll get $750/mo from the rental. Bump up to $10k a year to make the math easy. That's a 4% return, which is not amazing, but also not nothing - and you're already committed to buying/have bought the land, which is otherwise not going to return any monthly cash flow.
You could also finance the construction (maybe) and leverage things a bit if you wanted to, of course. Or build the house and then finance (probably easier).
Depends on your goals, really. This is not a situation where you can easily calculate a return, because too many of the numbers (ie future value of the property, sunk cost of buying the land, whether you're DIYing the construction and how much value you should assign your labor, etc) are a bit hard to define.
TL;DR - I'd go for it, since you already have the land.
-W