However, you shouldn't require a 20 foot setback for a pergola or a shed, so I wouldn't think the variance should be necessary for those items.

Also is your $300 a foot all in with land to turn key?

I'll foot stomp the trust piece mentioned by @Adam Bartomeo. 

I get MTR leads from Airbnb and do bookings through the airbnb platform.I use apartments.com to manage my Long term tenants and collect rent.What do I need to keep in mind for starting off on the right foot for book keeping?

Like putting in flooring is probably 1.50 to $2 a square foot for labor, and you can start to learn all these rules of thumb for all the trades.

Warren buffet used to say why jump over 1 foot hurdles when you can jump over 1 inch hurdles?

If you're thinking about turning your garage into a bedroom with a bathroom to make some extra cash, here’s the scoop based on my 20 years of experience: You'll need to budget for design and engineering costs, which typically run between $2 to $3 per square foot of your total property area, not just the garage.

Would it be helpful to connect with a local realtor that specializes in selling duplexes and their respective rents/ price per square foot?

And since this is an old house you will probably need to underpin the footings at the same time.  

I bought a house for 325k last year, a comp renovated 10 doors down is up for 540,000. 3/2 same as mine, 300 square foot bigger.