First thing you should do is read the bylaws. There should be some that define how the HOA should operate when it was incorporated. You don't want to break any bylaws. For two units I doubt it's that big of a document. You also should also get organized about all docs and record keeping especially if you have any sort of finances.

My understanding thus far is that we should build up our funds and then put some of that money in CDs and brokerage accounts, eventually

I don't know how much big of a budget you're going to have, but with larger HOAs like mine, we have operating costs and reserve expenses both with their own accounts. Reserve is for long term expenses like you need a new roof. Operating for paying things like shared landscaping. Reserve studies can help you identify how much time until you need to replace the roof or the siding or whatever other things are common with your building.

Don't invest in the stock market, but at a certain account size CDs for long term investments are a good idea. We use that to help offset dues increases.

It doesn't have to be complicated but you are technically running a business.