203k load and equity. Is my plan fool proof?

[Ivan Dushchenko]

Hello, bigger pockets community. I am starting out my real estate investing career, and I have a great plan.( or at least that's what I think). So the numbers below are raw, and they do not represent the exact values of the property, they are just to set an example. 

So If I go and buy my multifamily unit for $50000, rehab it for $30000. Now the dwelling is possible worth $100000-120000.  Because I only borrowed 80000, my equity is now about 20000-30000. Of course minus interest and everything else that goes into a loan. 

Now, is that equity mine, and would I be able to use it to get an equity line of credit ? I hope to make a deal like that, and use an equity line of credit, to get a second unit as soon as possible. 

If somebody has experience with 203k loans, and has free minute, please respond, because I cannot find an answer on the web. 

Thank you all so much, for all the inspirations and ideas. Love this forum