If you can't even get pictures of the interior that should raise red flags. 

The full rehab costs are closer to $35k with updated kitchen/baths, roof,hvac, interior/exterior paint. 

Here is a breakdown of the items they saw that needs attention.Needs minor trash removal; needs mownSupport post trim needs replaced; badly deteriorated; upper trim needs scraped and paintedBroken panes on side back needs replacedReplace fixture on front porch; flood lights on backNeeds some minor trash removed and minor work done220 wiring needs secured;not up to code, needs to be placed inside conduit.Install new furnace filterClean and paint register ventsInstall apprx. 4 door stopsFull interior rent ready cleaning required after all work completeReplace as needed to match all light bulbsSteam clean all carpet; sweep and mop vinylReplace missing storm door, paint interior doorPaint all wallsPaint door; interior shows signs of previous leak, but doesn’t appear to be a current problem; paint interiorSeal gaps in side window; paint all; seals appear damaged on double pane windows; may not be an issueReplace screensInstall two smoke detectorsInstall two blindsTouch up, as neededPaint all window sealsSeals appear bad; paintInstall screenVery old and drawers fall out; should be replaced with new; secure handles, if keptHas several large chips; functional sink otherwiseInstall two strainers Install fire extinguisherPaint side exit doorEstimated cost is $4,000. 

Or are pics of the interior on the website?  

I will be re-doing all the interior wiring so I just need to do the service and panel relocation.  

I’ve made substantial improvements to the property (flooring, texture, interior and exterior paint, total bathroom remodel, painted cabinets, new carpet, crown and base, new doors).

No soffets, no gutters, missing interior trim on all windows and most of baseboards, a wall completely in the way when you entered, washer/dryer relocate, no drain venting so rotten eggs overpowered you every time you ran water, etc. 

I bought one in LA County in a gated community earlier this year, that was built almost 15 years ago and needed some interior work, and the return on the work we did, in terms of both value and rental price bump, has been great, and the area is really growing.

My wife is a highly skilled interior designer.

In USD it amounts to $70,000 (unit price + closing cost + interior design & furniture).To cut the long story short, my total cash outlay amounted to $29,922 (which is 42% of the total unit value).