@Hae-Yuan Chang here is a BP Blog post that explains CAPEX reserves. https://www.biggerpockets.com/renewsblog/2015/10/13/real-estate-capex-estimate-capital-expenditures/You should also budget a minimum of $500 per year for routine or emergency maintenance.  

Getting the septic pumped is definitely on you and should be built into your operating costs as a recurring maintenance item.

On the flip side, you'll pay a prepayment penalty (yield maintenance) to exit early or the note will have to be assumed (which shrinks the buyer pool). 

I would add at least 1600 to what they claim for maintenance and they don't even have anything budgeted for maintenance.

There is much deferred maintenance and I believe rents could be increased to $500 with minor repairs/updates. 

Vacancies, inspections, pest control, repairs, maintenance, appliances, poor management, Section 8 abatements, and other things gobbled up my cash flow and caused me to have to empty my savings account just to keep up with things.

If you do go forward with it, before you lease out the land be sure to negotiate with the renter what they will be responsible for and what you are responsible for when it comes to land maintenance. 

That has to cover insurance, property taxes, vacancy, maintenance, etc. along with a cap-ex holdback. 

The upside is the maintenance costs go away for the most part.My personal opinion is just polishing the concrete slab will still look like concrete.

I would presume that if you have an absentee owner, there might be quite a bit of deferred maintenance, not just cosmetic fixes.