Once notice is given, it cannot be retracted or modified without land lord's express written consent." 

They have value solely through consent - the same as any other currency (including Dollars, Rubles, Yen and Bitcoin).     

You can sign the purchase agreement together, or just one of you can sign, so long as the contract incorporates the right for you to assign it to yourself and another investor(s), or some LLC or other entity prior to closing, and without the requirement of the Seller consenting to such an assignment.

I figure the realtor can do that legwork.I am guessing the trustee would be empowered to enter into contract with the consent of the beneficiaries. 

To expand on what @Joe Villeneuve posted above, you should form one ownership entity LLC to hold title to the property (if your Lender consents to an LLC owner of fee title) that is controlled by an operating agreement between two (2) separate LLCs as its members (one LLC for your interests, and one for your joint venture partner's interests).

If there is a mortgage, you will need to get the lender's consent to assign the mortgage to you, or you will otherwise need to refinance the property and simultaneously convey the property from your Aunt to yourself by a "no consideration" deed. 

If so, he can't consent to anything, only his mother can.Second, the only people that can do anything about the situation are heirs or their parents/guardians.

Do check your lease agreement for a sublease clause, but there's no mention of it, I would contact your landlord to obtain their consent.

However, when I went to sign documents, one of the forms my agent gave me was an acknowledgment/consent to dual agency. 

(I don't want to waste time building something if it doesn't at least make sense to some)Note: this isn't an advertisement, and I don't plan to advertise without consent.