Corporate insiders sell their own companies' stock for a number of reasons. They might need the cash for a big personal purchase such as a new house, or they might need the cash to fund a charity. Sometimes they sell as part of a planned selling program that they have put in place for diversification purposes.

Insiders, however, usually buy their own shares for one reason only: They think the stock is cheap and has tremendous upside.

Recently, a number of companies' corporate insiders have bought stock. These insiders are finding some value in this market, which warrants a closer look at these names.

GNC Holdings

Image placeholder title

One consumer goods player that investors are loading up on here is GNC Holdings(GNC) - Get Report , which operates as a specialty retailer of health, wellness and performance products.

GNC Holdings has a market cap of $564 million. This stock trades at a fair valuation, with a forward price-to-earnings of 6.4. Its estimated growth rate for this year is -37.2%, and for next year it's pegged at -5.2%. This is not a cash-rich company, since its total cash position is $34.46 million and its total debt is $1.54 billion.

The CEO just bought 592,259 shares, or $5 million worth of stock, at $8 to $8.49 per share.

If you're bullish on GNC Holdings, I would look for long-biased trades as long as this stock is trending above near-term support at $8 or $7.62 a share, then once it breaks out above resistance, at $9 to $9.23 a share, with volume near or above its three-month average of 3.3 million shares. Some possible upside targets are its next major resistance levels at its 20-day of $9.83 or $10.30 to $11 a share.

American Express

Image placeholder title

Another financial player that insiders are active in is American Express(AXP) - Get Report , which provides charge and credit payment card products and travel-related services to consumers and businesses worldwide.

American Express has a market cap of $73 billion. This stock trades at a fair valuation, with a forward price-to-earnings of 13. Its estimated growth rate for this year is 0.20%, and for next year it's pegged at 10.4%. This is not a cash-rich company, since its total cash position is $25.76 billion and its total debt is $54.83 billion.

A director just bought 4,000 shares, or about $318,000 worth of stock, at $79.73 per share.

If you're bullish on American Express, I would look for long-biased trades if this stock is trending above its 20-day at $78.99 a share, and then once it breaks out above $82.50 to $83.27 a share, with volume near or above its three-month average of 4.09 million shares. Some possible upside targets off that move are $87.50 to $90 a share.

Avon Products

Image placeholder title

One personal products player insiders are jumping into here is Avon Products(AVP) - Get Report , which is a manufacturer and marketer of beauty and related products.

Avon Products has a market cap of $1.9 billion. This stock trades at a cheap valuation, with a forward price-to-earnings of 10.7. Its estimated growth rate for this year is 600%, and for next year it's pegged at 50%. This is not a cash-rich company, since its total cash position is $654.40 million and its total debt is $1.89 billion.

A vice president just bought 150,000 shares, or about $655,000 worth of stock, at $4.37 per share.

If you're in the bull camp on Avon Products, I would look for long-biased trades if this stock is trending above support at $4.40 to $4.09 a share, and once it breaks out above resistance at $4.60 to $4.69 a share, with volume near or above its three-month average of 5.92 million shares. Some possible upside targets off that move are its 200-day at $5.16 to its 50-day at $5.34 a share.

Altisource Portfolio Solutions

Image placeholder title

One services player that insiders love here is Altisource Portfolio Solutions(ASPS) - Get Report , which is a marketplace and transaction solutions provider for the real estate, mortgage and consumer debt industries.

Altisource Portfolio Solutions has a market cap of $467 million. This stock trades at a fair valuation, with a forward price-to-earnings of 10.3. Its estimated growth rate for this year is -41.6%, and for next year it's pegged at -10.10%. This is not a cash-rich company, since its total cash position is $195.05 million and its total debt is $480.68 million.

A director just bought 25,000 shares, or $547,000 worth of stock, at $21.91 per share.

If you're bullish on Altisource Portfolio Solutions, I would look for long-biased trades if this stock is trending above support, at $23.50 to $22.50 a share, then once it breaks out above resistance at $25.50 a share, with volume near or above its three-month average of 311,907 shares. Some possible upside targets off that breakout are its 50-day at $26.88 to its 200-day at $28.08 a share.

SM Energy

Image placeholder title

My final stock with some big insider buying is commodity player SM Energy (SM) - Get Report , which is an independent energy company.

SM Energy has a market cap of $2.8 billion. This stock trades at a cheap valuation, with a price-to-sales of 2.43. Its estimated growth rate for this year is 41.4%, and for next year its pegged at 98.2%. This is not a cash-rich company, since its total cash position is $9.37 million and its total debt is $2.90 billion.

A director just bought 10,000 shares, or $256,000 worth of stock, at $25.69 to $25.70 per share.

If you're bullish on SM Energy, I would look for long-biased trades if this stock is trending above support at $24.43 a share, and then once it breaks out above resistance at $26 to $26.50 a share, with volume near or above its three-month average of 3.21 million shares. Some possible upside targets off that breakout are its 20-day at $27.66 to $29.30, or even its 50-day at $31.49 a share.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.