knowing people is different admiring their business is fine, however being part of an organization or organizing a team to work with is totally different aspect among friends. practically in past 30 years I have seen people losing friends & losing joint venture businesses for good.
what you can do is ask real estate friend to find you a nice piece of land at bargain price to build & sale a house.
after you have a piece of land offer it to your builder friend for construction & sale as joint venture under written P/L accounted for.
if that clicks and both people make reasonable money you can move on with same equation,
if it does not give you a reasonable return on investment try other opportunities without losing either of friend i.e builder & property dealer.