-- How many and which websites is it on overall?

They often have different vendors introduce themselves so you can build your team and they often have a local member do a case study on one of their properties to share the ins, outs, ups, and downs of the investment.

One of my associate mentioned that both me as a seller and the buyer can claim the interest paid every month, but I am not sure if that makes any sense. 

One of the properties is a three bedroom with no garage that the tenants pay on time but require more of my time than the others .

It would be helpful to me at this time, to have about $25K in working capital for work on one of my multi-family properties.

I've been surprised at properties that have passed conventional financing though...and even FHA....also, one could present 2 offers to seller--one for a cash offer and one for seller financing (at a higher price of course). 

My vote is option one.  

Connecting with local GC groups in your area will help you connect with subcontractors, find out tips and tricks of the trade in your local area (since all areas and their real estate differ slightly).Also, have you considered the motivation behind building a brand-new duplex versus finding one on the market?

One of my properties says it’s going to auction in March because it’s being foreclosed on.

If you want some revenue numbers for similar properties to the ones you're looking at or anything to use in underwriting feel free to reach out.