@Pavel Sakurets I'm a wholesaler in Dallas and have done both double closings (buy and sell on the same day) and assignments (transfer the contract to my buyer for a fee in lieu of closing).
I try to have 30-45 days to close with a generous inspection period to run the deal by my buyers.
To answer your other question: for me, I do not file Memorandum of Options on my wholesale deals, and I would not do anything to enforce the contract if the seller went behind my back. Why? Because it's just not worth the hassle and cost.
The solution is to develop great rapport and good ongoing communication with your sellers to make sure you don't have this problem come up in the first place. It would be because you lack this necessary rapport that you might encounter this situation, IMHO. If you have great rapport and communication, then your seller will probably tell you that he's really tempted to take someone else's higher offer, and you can try your best to get him to stick to the contract or work out another arrangement with him.
I think there's a lot of misunderstandings about the best practices with wholesaling, and I agree a lot of wholesalers throw out deals that suck. I try to subscribe to their mailing lists so I see some of the issues other investors are talking about.
Unlike some others, I think that people wanting to get started in RE investing SHOULD consider wholesaling, but they need to study and learn directly from the pros who are currently running solid wholesaling businesses. I'm still working on building mine up, but I have been helped so much by learning from others' experience and mistakes.
And yes, it IS possible to start wholesaling without much money or experience (driving for dollars and dialing for dollars come to mind). The difference is to make it work that way you have to invest a lot of TIME and SWEAT EQUITY to learn the trade properly to find and recognize the deals, and market or network with buyers.
I think there are a lot of investors who are happy to help newbie wholesalers, as long as the newbies are willing to work and learn and bring real value (DEALS!) to them.