After I sell my house I plan on renting for a while, but I eventually might want to purchase another primary residence in the future.

If you are thinking of flipping the place, you certainly can't pay more than the amount you would eventually sell it for.  

He' 4 yo now), get him trained on basic carpentry/construction and property mgmt. as a teen and eventually investing.

My motivation is being able to eventually be able to generate a passive income which would replace that from my job. 

I think it's best to eventually own, but it depends what your strategy is.

His girlfriend is currently studying architecture (bachelor's degree).In the future we are going to invest together and probably start a construction company/architecture firm.At the moment our plan is to build duplexes, fourplexes and sixplexes beside our full-time-jobs and eventually start investing full time.As you might can imagine we can put down a serious amount of sweat equity.

His girlfriend is currently studying architecture (bachelor's degree).In the future we are going to invest together and probably start a construction company/architecture firm.At the moment our plan is to build duplexes, fourplexes and sixplexes beside our full-time-jobs and eventually start investing full time.As you might can imagine we can put down a serious amount of sweat equity.

I'm trying to grow the real estate portfolio slow and steady and then eventually exit the corporate world to do real estate investing full time.I have not outlined the strategy/business model yet but am getting the ball rolling.  

I would stay away from New Ipswich, the school system is a mess.And school district matters if you are house-hacking a SFR, since eventually you will move out and want to rent or sell to families.Good Districts:  Hollis-Brookline, Souhegan, Bedford, John Stark, Hopkinton, Bow, Contoocook ValleyMiddling Districts:  Jaffrey-Rindge, Milford, Wilton-Lyndeborough, Nashua, MerrimackWould personally avoid:  Mascenic (New Ipswich/Greenville), Hillsboro-Deering, Monadnock, Manchester.

So, they do not have to be paid or paid back eventually with proper planning.