I would consider a minimum of 20% down as a reasonable down payment. Remember that the seller has to pay all of the selling expenses from this amount which will include a commission to the agents, title insurance, escrow fees and some minimal miscellaneous fees. This can total approximately 10% which initially leaves little left over for the seller. Also, the seller will be far more comfortable in offering you financing if they feel you have enough invested to really try to make a go of making your payments and not having to be foreclosed on.
In the event a seller needs to foreclose because a buyer they financed is not paying, this is a very costly procedure.
As far as assuming the loan I am not sure this would be the case. If there is already a loan on the home then you should ask to see that paperwork to assure that it is in their contract that they can allow it be assumed. Without this written provision, it may be illegal for you to assume the loan and if it became known the original holder of the note they could call it immediately due or there could be other serious legal ramifications. More than likely they are referring to the seller providing the financing and that is what I referred to above with the reasonable down payment.
Yes, the price would inclue the lot and I would assume it is less than 1/4 of an acre which is typical in that area.
Hope this helps!
Pat Sarcoz, Broker
White Mountain Realty