It all depends what you are trying to accomplish and the size and scope of the work:

If you are talking about an exterior work or window replacement, etc. the engineer or architect should be able to select the best companies and any other companies that you may recommend. In many cases, you may have 5-10 invitees to review the work and the RFP's or RFQ's. From those 5-10, perhaps 2-3 will end up providing bids depending on how busy the contractors project their schedules to be by the time you intend to do the work.

In other words, many will be called, but only a few will come through.

In small works such as a $30 - $75 K and depending upon the nature of the job job you may have 3-5 potential bidders and only 2 may respond, again because of the same considerations.

AdC

In our building, anything less than $1000 we don't bother with bids. If the cost is less than $5000, the board discussed whether we want to do multiples bids. If there's a contractor we've worked with before, and we like his work, we may just go with him without bidding.

For larger jobs, we do bids. AdC does a great job of laying out the details for those big projects.

Many managing agents have the ability to perform small repairs up to a certain dollar amount without board approval. Most of the time these jobs are given to a house contractor, super or regular. I have about three contractors that I use often, but I play them against each other to obtain a lower price/better job, etc.. I also on projects that I many not have experience in (where I do not know the pricing and protocol on my own), I will call in an outside contractor or two so I know I have everyone being kept honest (plus I learn). That is how I do it, but i have at minimum 3-10 projects going on at a time... so if you are a "newbie" to the contracting world, I would suggest obtaining 3 bids by sending a package to 5 contractors and create a spreadsheet and compare each item, apples for apples.

~AR