I have done 2 successful flips and also have one 1 buy and hold.Now that I have a little skin in the game I’d like to ask my dad who is 62, with a 6 figure 401k to allow me to use $50,000 to invest in more real estate.

You asked if HMLs will roll renovation costs into the loan and the answer is yes but unless you have experience and a track record, they will want skin (your skin) in the game. 

Ive got no skin in this one, but i like the building and I'm looking all the time. try to find other 1500 sq ft in delray.

For a GP to have "skin in the game" means they will be as cognizant of the consequences and at the worst case they will at least try to protect the investment because it protects their own equity (as well as that of the other investors, which should be the GP's primary concern as a fiduciary).

But since there is no longer a house they want me to pay an additional $120,000 skin in the game! 

Someone who has some skin in the game in your success

There are multiple ways to skin this cat.1) Create a new LLC with identical ownership2) From the "old" LLC distribute TIC interests in the improvable parcel prorata to all the members. 

But since we have a good relationship, he’s someone I trust and like the idea of giving a partner like that some skin in the game to be incentivized to get things done efficiently.  

With commercial loans using community banks I've seen they usually want to see skin in the game.

The buyer needs to have some skin in the game (unless the purchase price is WAY under market).