I have a lot of experience with septic systems. Engineering standards are typically very strict, so your 2007 house should be fine, but get it inspected anyway. My problems with systems have mainly been with the filters. There is a filter between the tank and the leach field, which protects the field. If the effluent has things floating in it that would clog up the leach field, the filter catches it.
The field is very expensive to replace, so you must protect it and not remove the filter, even though it's tempting because the darn thing keeps getting clogged. Items that clog the filter include cat litter and coffee grounds. It's very easy to clean the filter, but gross! When the filter is clogged the water level in the tank rises. This causes a back-up into the home. In freezing temps, this back-up can freeze, causing even more problems.
I have multi-units that share a system, so I can't prove which tenant caused the clog. I've threatened to do DNA testing, haha! The first floor tenants have an incentive to be careful because they get a wet bathroom floor if it backs up, but they are at the mercy of the upstairs tenants. However, if I had a house I would make it the responsibility of the tenant. If they flush it, they pay to clear it.
Another thing, you need to keep the system, including the field, free of trees and bushes, so it must be mowed regularly.
As long as the tenants are careful, they will enjoy not having to pay a sewer bill!