A concession is primarily for the buyer(s) benefit, it can help seller(s) to sell a property but there is really no advantage to a seller accepting an offer with a concession except that it is incentive for the buyer(s) to focus on that property, it makes the terms more attractive. 

I would like to have a loan calculator in order to do offers with out using mortgage broker before have accepted offer.

Credit score is acceptable, he has no evictions, have enough income to cover rent comfortable. but then i am here as it's useful to learn from others experience for this kind of profile and background that I have no experience with.   

Investor Beware....Once you jump through all the hoops and prove your salary and net worth, make sure the credit of the borrowers are within your acceptable credit range.

It sounds like I should wait until mid to late next year at least to accept any offers.

Bottom line - All hype, bs, misinterpretation, opinion bias, etc aside, sellers willing “owner finance” the sale of their property for one reason - and one reason only: They PERCEIVE that they are getting a higher price for their property by owner financing than by a cash (cash to them) sale.The “perceive” part is why buyers can sometimes structure terms ridiculously one sided in their favor - because some sellers are so focused on PRICE they become oblivious to anything else.It’s why I and numerous others have been able to structure 20 year owner financing loans at ZERO interest; why sellers have accepted “substitution of collateral” that gave them a lien on recreational land I had rather than their own income producing property; why sellers accept second position liens and allow buyers to obtain new first mortgages ahead of theirs (subordination), and why sellers always accept mortgages without my personal guarantee.I myself sell properties and provide owner financing to obtain a higher price.

That is acceptable by our fire dept in Denver that inspects it once a year. 

Beyond removing the developable parcel from existing loan expect whomever finances the construction to want zoning, building permitting and utility connection approvals before the loan is originated (some will accept just zoning).

This reminds me about the other day when I heard some agents debating about if you should accept less than 6% and one of them had the audacity to say "you wouldn't negotiate with a doctor would you"... like gtfo!

After giving notice to vacate or filing an eviction suit, Landlord may still accept rent or other sums due; the fling or acceptance doesn’t waive or diminish our right of eviction or any other contractual or statutory right.