I've seen folks claiming conservative underwriting because they're supposedly using conservative comps for rent assumptions, whereas in reality the comps were totally unrealistic, and were located in significantly nicer neighborhoods. 

@Denise James The seller sees you as a sucker they can take advantage of, It's up to you on whether you want to make him right or wrong about that assumption.

My numbers and assumptions are below. 

My initial assumption is that at minimum we will need landlord and liability coverage; does landlord cover fire as well?

I am making many assumptions here, but I am mostly assuming that you will need the cash flows from the $30-$250k to live on.In my opinion, the stock market is too volatile and if we have a sudden downturn you may not have enough time (thinking 10 yrs +/-) to recover from any drop while maintaining your current standard of living.

He said that mortgages are registered and by making the assumption it was a 30 year loan, you can calculate the amount paid off.

The foundation repair company salespeople (and even owners, in some case) of structure companies are not engineers and though they may be right most of the time, there will be gaps in their assumptions.

An additional upside is not included in the underwriting (upside from the laundry room).Assumption Loan is approved for 79% LTV.

I'm not really clear on the question.You have a $75k mortgage, doesn't matter what type.You apply for a $105k cash out refi on the assumption that it'll appraise for $150k.

Make sure you check accurate rental rates for the area and property types you are looking at, budget out appropriately, and don't make the assumption that because it's "turnkey" that you can budget minimally for capex and repairs.