@lyihjl-hotmail-c , while agree with my colleagues @xmasbaby0 and @M-MTax on the gift tax info. I don't understand your statements :
(a) " buy his house for my side as well as his side" -- are you trying to buy a property together or what ? Is this a loan to your brother or what ?
(b) "without tax issues" ---- generally all the monies you have after paying taxes, i.e. post tax monies -- is your money. Whether you gift or loan there is no tax on it. Even if you gift above the free per year/ per donee amount it does not attract any tax. The reason you need to file a gift tax form is for amounts greater than the free limit is accumulated throughout your life for purposes of Estate/Gift tax reconciliation upon your demise i.e. against the lifetime tax limit ( of 1 million , I think ). Unless you are super rich, most of us will never get there.
Hope that settles your query.
