Here is my bind, my sibling wants to sell the house to me at a valuation of 390k.

Cause someone's elderly parent to pass away due to lack of professional care and you are in hot water.With that being said, my sibling owns an ALF and I helped put the deal together.  

I have property that is jointly held with my siblings.  

Maximum financing however, is available for: Borrower related by blood, marriage or law, such as - Spouses - Parents-children - Siblings - Stepchildren - Aunts-uncles and - Nieces-nephews or Unrelated individuals who can document evidence of a longstanding, substantial family-type relationship not arising out of the loan transaction.

Maybe it's time for Yu to have a talk with a real estate attorney to keep himself out of potentially hot water with the IRS as well as the owner or his siblings suing Yu's behind some years down the road.

Also the plan is to split the sell of the house with me and my siblings, will we have to pay taxes on that money (around $20,000 each)?

Most banks won't be that eager to lend to an 18 year old but if you have had a consistent job in high school and continue to work throughout college, then it is not impossible.You could also have a parent, older sibling, etc co-sign on the mortgage and that would allow you to get around the financing issue.

I grew up in Tampa, plus one of my siblings is an agent in Tampa.

His grandparents and Mom all passed leaving several properties to four siblings, one of which has schizophrenia.

And every family member is different, including among siblings, believe me, I have ten brothers and sister,  and we all have different habits in cleanliness and standards in life.