Mortgages have more favorable terms than HELOC's (longer amortization, lower payment) so this may be a better option if you have a set use for the funds.However, HELOC's offer added flexibility that mortgages do not because you do not pay on them if you do not use the funds.

It is fully customizable and flexible. 

They have a lot of flexibility in their underwriting guidelines, so the 2-year thing may not be an issue. 

So my thinking is in order to keep maximum flexibility with the scenerio here it really needs to be 50% you, 25% brother and 25% father to make things easy.Am I thinking right or am I lost?

I thought about using it for only the 20% down, but it seems I'd get more leverage/flexibility if I just paid cash outright, then had a great asset to borrow against! 

I have a strong relationship with a regional bank that provides me lines of credit as well as flexible loans where my interest is generally prime +1% or prime +2% depending how I structure it.  

Credit unions have their own funds not Freddy's so they can be somewhat flexible and make their own policies like the deals above. 

The key for us with our business plan was flexibility.

Sometime you have to be both flexible and courageous when it come to investing.  

I generally like to use the most popular, flexible, free themes available.