How do you buy land and sell blueprint prior to construction?

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Good evening everyone, I am new to the forum. I am currently a university student who is studying finance and working part-time as an accounting clerk making slightly above minimum wage. As of right now I have about $2.5k in my bank account but by the end of the summer I could probably get it up to $5k.

It seems that through my quick browsing there hasn't been too much written about this... How would I go about finding land, getting a contract on a single-family house blueprint (usually these go for a lower price than a ready home), and then construct the home based on what you sell this blueprint for and keep the difference? 

Ex:

Buy land (or mortgage for land) for $15k     

Design or buy a ready blueprint for a single-family home 

Interested buyer decides that he/she wants the home constructed that you designed and pays you $500k to do so

You hire builders to build you the home for $400k

You the difference ($500k-$400k=$100k)

(the numbers I used are purely hypothetical to show what I mean).                                                                                                                                                                                                      

Also, is it possible to do a sort of 'wholesale' on land so that you can seek out interested buyers for your blueprints prior to actually putting money down for the land?

Sorry if this was too long or I wasn't very clear with what I meant. I live in Illinois - if that makes any difference. I really look forward to your input!