Size and number of hard drives for new 4 bay NAS?

[Slush]

I am planning on buying a DS920+ for home and business use. I run a software consulting business from home. Typically only 2 people will access the NAS and our storage needs are low (no plex, video, or surveillance needs). I chose the DS920+ as an investment in something that is scalable that I won't need to upgrade for a long time. (Tell me if I should reconsider this.)
Considering I currently have low storage needs, what is the best strategy for hard drive selection? Do I populate all 4 bays with hard drives or only 2 or 3 bays? What size do I buy- the largest I can afford? Do I buy the same size for all hard drives or maybe 1 large and 2 smaller sizes? Ideally, I spend no more than $600 USD (around the same price as the NAS) for hard drives. How do I best allocate this?

[Norm]

I believe the first step is to try to figure out about how much storage space you think you will need. If you don't think it is going to be all that much, say a TB or so, I'd just get 2 drives about 4-6 TB in size and mirror them. If you get two 6tb drives and mirror them, you end up with 6tb of usable space. For most folks that's quite a bit of storage. If you find that in a few years you start filling it up, you can swap them out for larger drives. Prices for larger drives a couple years from now will be far less than they are today.I personally like mirroring (Raid 1) much better than Raid 5, 7 or 10. With only 2 drives, there are far fewer things to fail or go wrong, they produce less heat and noise plus they use a lot less power to operate. If one drive fails, take it out, pop in a new one and the system will rebuild the new drive.

[Slush]

Thank you!