Triplex - Should I add another unit????

[Ida Powers]

Hi All, 

We currently own a triplex, it's basically a duplex with a small single family sitting behind it. The property has a slab that I think was used for a basketball court at one point and we measured that it could fit a 1400 sq ft home on it. At one point, the property did have 4 unit but it was on a different part of the property, not on that same slab. What do you all think about a manufactured home on the slab? I found some for 70K - 100K. I think I could get about $1200 in rent. Would a manufactured home make the property harder to sell in the future? What other things do you think I need to consider?