2) What investment strategies do you use?

Tax mitigation strategies for sale of rentals include 1031 exchange, Sec 121 exclusion, Qualified Opportunity Zone, more things, ...

There are a couple strategies to have your offer be very attractive and still be able to use your lower down payment loan. 

Is anyone willing to share systems or strategies their brokerage/firm currently uses? 

If she is already meeting these tests it may be a great tax strategy.

While working with investors I'm learning as much as possible about their different strategies and taking thorough notes so I can develop my own.

Is a solid long-term strategy.

Here goes:I am planning on buying my first foreclosure and will be using the strategy of full cash offer via the HELOC that I pulled out a few years back.

You can get stuck in just determining which real estate investment strategy to use. 

It seems to me that because you are going with the new construction route, with the bulk of the down payment provided by your grandparents, you would be missing out on this key benefit of the house hacking strategy as I bet the lenders are going to require a minimum of 20% down.