Yeh if you just buy a fat pump and some plastic plumbing pipes/t-joints/silicone you can EASILY make an Ebb n Flow system...but for 40 plants a strong pump is essential to get a the drink all the way up the pipe to every plant...But its piss easy....large hydro systems are convenient and pretty to look at...but they are bloody expensive!!! all you need is the above and timer which should cost peanuts..the main part of you budget should go into the things u cant really do yourself ...like make a light cooler and squirrels and carbon filters are dear but 'must have'. I have a 400 watt that kicks out 55000 lumensso two 600 watts should do nicely...get some metal halides for the veg room if you want denser buds that people will buy ...a few cool and warm white fluoros will suffice for the clones untill the are ready for the metal halide!! Happy Days