I also walked the property at this location and found it to me in excellent condition.

always 20% or greater. we do it with our profit in columbus OH. it's all about the land, density, and floorplan size. get someone who has more experience in design and agency and development. development has been doing this for years and years so just stick to what works. compact, three story walk up style is what we build for investors and ourselves. 

I happened to be away for a wedding out of state, so i had my Agent and Contractor walk through it together. 

I am pretty confident that with $30k down on a $116,000 property, plus the buyer himself has good credit, that he is not going to walk away from this property.

Because they are undermarket, most mom and pop or uneducated 'investors' will just see it for what it is, maybe they'll run some simple numbers, and ofcourse the numbers with the below market rents and the now new purchase price don't likely pencil out and so... they will walk away and keep looking and are usually the ones complaining that 'it's hard to find any good properties in today's market'... where in fact that is exactly where you as a savvy investor make your money. 

I raised about half the money personally by giving 30 to 60 minutes of my time for donations And when folks would ping me and I would ask for 100 or 200 and I will spend the time on the phone and walk you through how to do that sub to deal or how to do notes or what it takes to develop land etc..

I hate to walk away at this point as my apartment lease ends in a month but I also hate to get screwed.

Because there are a lot of sponsors with experience (which varies) who are in the middle of capital calls, raising pref equity or just walking away from deals or losing deals.

Prior to sheetrock and after final inspections, walk through the build out and make sure everything looks correct and there won't be any issues later.  

Your contract should have a due diligence/inspection period that allows you to walk away with your earnest money but if you miss that window you could be out whatever you put as EMD.