Welcome David.
You are living from check to check from the government, yet you are considering a $6,950.00 dome!
http://www.homedome.com/store/product_10ft_domes.htm
You could build a very spacious roll-of-roof obs for under half that cost.
or even buy a ready built Roll-off-roof obs fully installed from places like this starting at $2,960
http://www.backyardobservatories.com/