Originally posted by @Amit M.:
I have also been wrestling with this exact question. The first thing is that it really depends on your market and the rents- the higher end the market, the more important the amenities are.
I own property in San Francisco, so like you are in an expensive market. One duplex I have will need to gut remodel. In this case it much easier to invest in all the necessary plumbing and electrical needed. Plus I have space near my bathrooms, where all the plumbing passes by anyways. But even so, I expect it to cost me $2500-3000 per apartment (incl. the WD units).
In another triplex I just brought, there are new coin op WD in the garage. To be honest I'm not sure how much of a turn off it is for tenants to share the machines with 2 other couples in the building. But I know in this case that it does not make sense to go in the units. I'm trying to get a sense from new perspective tenants.
I am trying to figure out how a gut rehab of an apartment can only cost $2,500 to $3,000, including a washer and dryer and Refrigerator, and stove, and dishwasher, and kitchen cabinets, and counter tops and tile floors and bathroom fixtures, and painting, and electrical, and plumbing. Come here and do that for me for $3,000.
About your Triplex with the machine in the garage, perhaps when one unit is empty you can try the w/d "en suite" and charge the $50.00 extra and see how it goes.