[eqvinox]

You want outdoor-rated (longitudinally waterproof) single-mode fiber, with steel or kevlar braid. If it costs about 50…80ct/m (not including termination cost), you're in the right ballpark. It's possible to go cheaper, but then you need to know what you're doing, which by your question you don't ;-)

If someone is trying to sell you multi-mode fiber, they're 20 years behind the curve. (No, the transceivers are no longer notably cheaper.)

If someone is trying to sell you unarmored fiber, they want another sale after rodents chewed up your first fiber ;D

For waterproofing, note there's lateral and longitudinal waterproofing. You want longitudinal, otherwise the fiber can pull water like a hose straight into your patchpanel. (It's rare but it happens.)

Cheapest source I know is fs.com, for an outbuilding office order something that comes with connectors preattached (and add a good amount of slack). Splicing on connectors by any reasonable professional calls up mind-boggling hourly rates.

[organsnyder]

I bought a 12-strand single-mode pre-terminated cable from fs.com. I don't remember if it's armored, but it is in conduit for the whole outside run. 12 strands was only slightly more money, and it gives me tons of flexibility and future-proofing—even if I'm normally only using a single pair. For instance, when I upgraded from 1GbE to 10GbE earlier this year, I was able to utilize a second pair to do the upgrade in stages (anything to avoid disrupting my kids' Minecraft server connections...).

I think the total cost for fiber and transceivers was under $200.