with a Worcester 3 Decker you can modify the layout, add a BR or a BA but you have to know what can easily be done. 

Your local jurisdiction may not require stamped plans even if you are doing a larger remodel including modifying load-bearing walls; however, then the liability and safety compliance becomes your responsibility.- What type of help do you need?

Guest got so offended, and said they will contact airbnb to change their review... after I wrote a review for them (thinking that it is imposiblle for review to be modified after it was submitted) guests review was posted on my account, clarly modified saying how I requested additional payment after they checked out.

We've modified our rental agreements over the years to suit our needs.

I just wasn't sure if it was known that they always modify it somewhere like certain pages.  

We even modify apartments to make it easier for them, such as installing comfort height toilets, grab bars, handrails at the front step, and good lighting (inside and out).Good luck!

Offer to modify the terms to include interest or a piece of the profits.

SEC docs are not cheap, but can be modified and reused for other deals in the future. 

But to your question:Your income = 3,000/moBuy 1M house, 500k down/equity 500k loanRefi to 750k loan, 250k equityRent other units at 2000/mo/unit (say 4-plex, rent 3) = 6,000/moNew modified income = 3,000+6,000 less expensesBuy 2nd unit at 1M, 250k from 1st house refi add 250k more (750k capital exposed) ... 500k loan, 500k equity/downRefi to 750k Rent 4 units at 2,000/unit/moNew modified income = 9k + 8k (2nd prop) less expenses........ repeat steps until capital runs out.

Anyways great news is I am still making well, and honoring my original (but yes modified in writing) agreement.