In Mass. you can not put any screen printing chemicals down the drain, no matter what the label says. You can not use a filter system on the drain either before the septic. You will need to have an underground holding tank (1000-3000 gal) it cost about $1500.00 for the plans. The plans, tank and installation can cost up to $7500 depending on the area. Any civil eigineer can make the plans.They might make you put an alarm on it so it will not overflow. The only thing that goes down the drain into the septic system is human waste and grey water (clothes washing machine...) It is also against the law in MA. to discharge the drain of your clothes washing machine to the outside, it has to go in the septic. It can cost up to .60 per gallon to have the tank emptied. How many times depends on how busy you are. If you are working out of your home you will be dealing with the Federal, State and Town Goverments which means paper work, inspections and of course fees. Fees could be up to $1000. per year to show you are in compliance. Make sure you can have a home business in your town. Start doing shirts for a Septic Co.
This is what i have for a work space next to my house, garage level 1200 sq feet (production), second floor 750 sq feet (office with A/C) also stand up attic for cold storage. I built a 3 BR house next to my 3 BR house with a very big garage door. I have 6/4 Hopkins, 6/8 Gauntlet and 12' electric dryer. Hundreds of screens on racks floor to ceiling. The ink, exposure and washout rooms are small. Very little room for any inventory storage. For electrical i had to split my 200 amp service and bring 100 amps to the shop. Bigger is always better. In the summer months many boxes are stored outside during the day and you hope it does not rain. If you are in a residential area maybe look for properties that a 2 seperate deeded lots next to each other that way you( i think) can have sepaerate meters to the lots (200amps) each.