question about equity

what if you built a duplex yourself for 75000, and it appraised at 150000, would it be possible to borrow 75000 against it? Then sell the 1st one, and borrow against the 2nd one to build 2more and so on. any thoughts on this appreciated thanks

if you can do that, then by all means do. try it, so what if it isnt worth twice as much after its built, you can still make some $