Seeing an old hvac, water heater and AC units are obvious items unless there were unforeseen issues with them found only after inspection.You can put a dollar value on these items fairly easily, but just in HVAC/AC, water heater you are going to be reducing your offer by a substantial amount.

You need money for repairs, reserves, and unforeseen big-ticket items.  

I did plan for some unforeseen repairs as well but there were just quite a few more than I anticipated.

Some of the most standout things had to deal with making sure the numbers are correct on the front end so that if unforeseen expenses come on the back end it will all be covered.

Also, start the refi process before the project is complete so you can plan for any unforeseen circumstances that may delay your closing

I have to put the kitchen together and take the trash out but unless something unforeseen happens with paint and carpet contractors, we're going to finish ahead of schedule. 

I would like to preserve this capital for the unforeseen issues associated with fix and flip.

(III) any other period of temporary absence (not to exceed an aggregate period of 2 years) due to change of employment, health conditions, or such other unforeseen circumstances as may be specified by the Secretary.Also- It's important to keep in mind that you can only utilize a 121 exclusion once every 2 years. 

Even in today's low interest rate environment, it is smart to leave a margin of safety (error) so you can absorb the unexpected or unforeseen. 

I am a newbie investor (mid 40s), currently working long hours in order to save for a large down payment on a distresses multifamily, plus have a decent reserve for unforeseen rehab costs.