Do not just sit with unleased tenants.3.

And you're sitting up there with an asset that you bought for 150 000 you've lost 100 000 in equity and your cash flows are depleted.

The home is sitting on enough land to either expand the home greatly or add a duplex or another small home in the future.Just seeing if I made the right choice.

It still sits vacant to this day 40 years later.  

Are they motivated and do they have 100,000 sitting in their bank account?

It has a huge center center chimney that sits on an extremely large fieldstone foundation that takes up most of the basement.

I recall until a year ago, they will do HELOCs on investment properties only if you have 4 or fewer?

3) If it just sits in the investment account, can I still accumulate taxable interest year after year until I use the cash for an income-generating property or stock?

There are actually different ways to buy with "cash"... the best, and the best way to BRRRR, is having 100% your own, literally sitting in your own checking account. 

With 300k you may be able to do 2-3 at a time. after you get to about 10-12 see where you are sitting cash flow wise and if you feel like it is too hard to manage look to 1031 into a bigger complex.