With the issues you described it sounds like this may be a tough deal for a first timer unless you are getting the place at an absolute steal.Something to consider: Will the rehab costs you are walking into drain your reserve funds?

It is right beside the drain, spread out in an area that's about 3" x 3". 

Laundry room will have a washer pan with a drain to the outside with tile floors. 

The unknowns I have had to learn the hard way are everything you can not see using one point in time (pre buy inspection); i.e. subfloor wood rot in your crawlspace that no one caught (even though 4 people were down there at different times), permits (have people pulled them in the past for big things that were done on the property), septic drain lines (septic tank was amazing, but the drain lines were faulty had to get a permit and get the city to do an inspection and called for a 7,500 repair and partial mound system to be installed....when the original inspection and pump was aok because it was a dry time of year)...., speaking of time of year, a HVAC unit that was inspected in the winter and the differential was AOK, was inspected for a closing in the summer and had to be completely replaced (4k-that I wasn't supposed to have to spend), drainage issues on the property and water intrusion......no body really inspects for drainage issues prior to closing, especially when it's a dryer time of year, then BOOM the rain hits and water is coming in over the foundation because water is not being routed correctly around the house.

Is it totally unfinished with a drain in the basement floor?

What you will find out is people will not treat your house as good as you do and your emotional attachment to this home is going to drain you and probably ruin friendships along the way.

As soon as I and renewed the lease the tenant wrote me this long message with all these thing wrong, including drain smells bad(she’s been putting bleach down the drain to kill the odor, the lights in the kitchen and bedroom are flickering(this ones easily fixable) & the bathroom floor is in-caving because of water damage(she suggested a new shower door).

I am considering a property that has great numbers, but the 4 building complex has septic issues like:  drain-field, "bubbling" due to renters putting "6-7 people" in the apartments, etc. 

It is emotional draining even if you win though.

Managing more than 1 very low income property is a serious drain on time for an investor in most cases, but the trade of is typically the cash flow on paper numbers are better which draws people in to these investments.