Should I add another unit?

[C Niman]

First I want to thank Josh and Brandon for creating this fantastic website. There are a lot of amazing people here and I cannot be more grateful.

I have a rental with an empty basement. I want to create more income from this property so I want to turn the basement into a rental. (Duplex) It is approx. 28 x 60. I would like to build a two bdrm but not sure where to start. Yes, only a two bdrm, as i suspect i will have problems with egress. Top floor is a 3 bdrm 1 bath but in the spring will be a 4 bdrm with 1 and a 1/2 baths. I understand I may have to upgrade septic (tank in ground) and add another meter for electric. Water is from a well on this property. This rental is unique. It is two mobile homes placed on a full foundation under one roof. I added this information because I'm concerned about putting too much money into this project. If I add this rental, I will raise my profits by $500 per month. My question is, should I take this on and if so, where do I start? Prop. Is located in rural PA. on one acre. Thanks in advance.