Laying the fiber costs something like $1,000 per house and your uplink will cost over $2/Mbps/month (fortunately you can oversubscribe it 100:1 or more). That's not counting any of the equipment.
Laying in the fiber is a sunk cost, so that shouldn't be the biggest issue.
At two dollar per Mbps oversubscribed 100 times is $20 for each user/month, sell the service at $70 month, and you should have enough to turn a profit, pay back the investment and keep the thing operating.
At two dollar per Mbps oversubscribed 100 times is $20 for each user/month, sell the service at $70 month, and you should have enough to turn a profit, pay back the investment and keep the thing operating.