One good deal with healthy margins will make it worthwhile. 

I have through my brother a healthy stream of investors which I believe positions me in a better position than most wholesalers.

I think you may struggle finding a healthy and strong tenant pool @ $1400 a month (personally I wouldn't buy a $150K property for only $1400 rent).

I figured a wholesaler probably had a healthy markup and could stand to accept a smaller profit on a property that's sat on the market for over a year. 

Opened a revolving line of credit for $200,000 against the equity in the house and just recently used it to buy my third property.It seems the market is still very healthy in the DC/MD/VA metro area.

Ali:A pretty blanket statement which would be akin to someone saying prices are too high in the entire U.S.A. to support positive cash-flow.There are lots of markets in Canada in which a healthy cash-flow is possible - naturally Vancouver (BC) and GTA (On) are not two of them at the moment - some where, with a little perseverance, you can even see cash flow at a double digit rate.

Even with the recent run up in prices that cap rates for multi-family are still pretty attractive and the returns are pretty healthy.  

I would have financed as much as possible to still have a healthy cash flow.  

That is a good sign of a healthy market. 

There are no guidelines other than a little healthy sense and good negotiating skills.