If you want to do it yourself then there are some good resources on this site for helping you to learn how to do that effectively and efficiently (I'd start with some of the podcasts and also read up on the books they recommend on the show notes).

In an efficient market, you can not make above normal returns in the long run. 

Besides, these days an energy efficient home is more attractive than an identical looking home with replacement parts. 

Business Plan (6/23/2016)Mission Statement:I strive to convert real estate properties that have become burdensome for current owners into blessings for new owners and tenants through various investing strategies such as wholesaling, fix-and-flipping, and buy-and-holding.Goals:Short Term (Over the Next 5 Years)Do my first wholesale dealForm an LLCGet my real estate licenseContinue building a funnel of leads that brings in 1-2 wholesale deals per monthStart building a portfolio of buy and hold propertiesPurchase our first primary residenceEstablish a team and marketing machine so that I can start confidently and efficiently operating with other strategies such as fix-and-flipping and buy-and-holding to generate more monthly deals, and faster and continuous capitalLong Term (Beyond the Next 5 Years)Build a portfolio of rental homes that are cash flowing a combined passive income of at least $6,600 monthly (33 units bringing in $200 monthly or some other dollars per door equivalent); I believe then I will have achieved financial freedom.No longer being restricted by HAVING to work full-time for someone else, I want to devote all my time and money to my family and using my God given gifts and talents to build relationships in which lives are transformed by the Gospel of Christ, and continue building passive income to fuel these endeavors until I die and the legacy is passed down to my childrenStrategy:Starting off, I plan to raise capital via wholesaling.

In my experience this is the most economical and efficient way to fund deals. 

A more efficient system by far IMHO.  

Are either particularly cost efficient for specific tasks?

I find that I can do $250 per month on a $50k unit, certainly this building will not get me to that level, but there is also the efficiency of being able to hand off management being all the units are in one place. 

There is an efficient process to follow with steps where you go deeper with due diligence at various stages ( initial inquiry, LOI submitted, purchase and sale signed ).

And also if you'd rather PM me so we can communicate more efficiently that'd be great.