We inherited a non-functioning gas gravity unit as part of our recent purchase...

That seems to be the thing to do if you’re out-of-state, so your holdings have some gravity.

They're almost a universal constant, like gravity and problem tenants.

Personally I don't like a non-gravity solution as a power outage and you have backed up sewer again.Another solution is to use trenchless technology. 

I believe both men were wearing leather sole dress shoes on a pitched roof, when gravity took them on that final ride.A couple of owners later the house burned and was a total loss, which solved the roof problem.So where I'm going with this, is if there is an easy access point to the roof, you may get sunbathers, partiers, adventurous teens up there monkeying around with the HVAC equipment (in addition to the droning humming noise).Good Luck!

Currently have interest.Questions are:     -Property topography does not permit a gravity sewer connection. 

it's all about the Content these days.My custom website cost me over ~$4000 after 18 months from hiring out the SEO and Content, buying a template and some plugins (Gravity Forms), while over the same time Carrot cost me $900 (that was actually for 3 sites as well Seller, buyer and Company).To get to your point about Renting Vs Buying.  

The current situation is an example of this.The ease with which someone can post online on various platforms belies the gravity of some communication.

General note ... there are dozens - maybe hundreds - of different on-site wastewater system system types, from basic "conventional" septic systems with a septic tank and gravity driven leach lines to complete package treatment systems (like a miniature municipal wastewater treatment plant).

I renovate to create a bullet proof, durable dwelling and always include a few basic frills (tiled tub surround...refinished hardwood floors...mini blinds on the first floor)I always remove obsolete items like gravity furnaces (love used 80% efficient units and used gas water heaters...I'd drive a hundred miles to pickup a truckload at the right price) and definitely remove cast iron tubs with those silly ring shower curtains for new tubs with a shower head.