On first look, the plumbing looked modern and good (no idea on sewer). 

Than spend more money on the method that works and quit wasting money on math instead don't

You do need to be creative, methodical and ethical.

We did live in the property during the whole reno, at times we were limited to one room and there were several times when we didn't have electricity or plumbing and have to improvise or stay with friends. 

Technically if you have a decent sized upstairs you can turn your basement into one with a small amount of plumbing and electrical work.  

They cover major issues with plumbing and electrical too.Cons: Cost to cover major things in your household is about $635 per year.

The contract shall contain at least the following provisions:(1) The full names and then current mailing addresses of all the parties to the contract; (2) The date when the contract was signed by each party; (3) A legal description of the property conveyed; (4) The contract price of the property conveyed; (5) Any charges or fees for services that are includable in the contract separate from the contract price; (6) The amount of the vendee's down payment; (7) The principal balance owed, which is the sum of the items specified in divisions (A)(4) and (5) of this section less the item specified in division (A)(6) of this section; (8) The amount and due date of each installment payment; (9) The interest rate on the unpaid balance and the method of computing the rate; (10) A statement of any encumbrances against the property conveyed; (11) A statement requiring the vendor to deliver a general warranty deed on completion of the contract, or another deed that is available when the vendor is legally unable to deliver a general warranty deed; (12) A provision that the vendor provide evidence of title in accordance with the prevailing custom in the area in which the property is located; (13) A provision that, if the vendor defaults on any mortgage on the property, the vendee can pay on that mortgage and receive credit on the land installment contract; (14) A provision that the vendor shall cause a copy of the contract to be recorded; (15) A requirement that the vendee be responsible for the payment of taxes, assessments, and other charges against the property from the date of the contract, unless agreed to the contrary; (16) A statement of any pending order of any public agency against the property.

No plumbing, electrical, windows, fixtures or mechanicals.

What payment method do you allow?

First was HVAC, then plumbing and electric--I do not leave those items to a handyman.